TurboC Notes

8/11/2019 TurboC Notes

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Computer Programming 1Turbo C


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What is computer Programming?

Computer programming is creating asequence of instructions to enablethe computer to do something.


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What is a programming language?

A programming languageis anartificial language that can be usedto control the behavior of amachine, particularly a computer.


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Programming Language Translation

Source Program -- program written ina high-level programming language.

Object Program -- the source

program after it has been translatedinto machine language.

Translator Program -- the programthat translates the source program

into the object program. Can beeither a compiler or an interpreter.


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Compilers vs. Interpreters

Compiler -- spends some time evaluating theentire program and then translates all theprogramming statements of a program into amachine language program, which is then

executed at once. Interpreter -- translates interactively each

programming statement into an immediatelyusable machine language instruction. Although aninterpreter slows down the execution speed of aprogram somewhat, it does not require extra stepsto compile and link like a compiler.

In a production environment where throughput ismore critical, a compiled language is preferred.

Any high-level language can either be interpretedor compiled.


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Categories of Programming

Systems programminginvolves writingprograms that enable a computer to carry outits basic internal functions as well as some

other specialized functions. Examples ofsystems programs include operating systems,device drivers, and utility programs.

Applications programmingrefers to theprocess of developing programs to be used for

specific applications, such as a businessapplication (e.g., computing benefits to bepaid to different employee classifications) oran academic application (e.g., determiningwho qualifies for which scholarship, based onspecified eligibility criteria).


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Stages in the Applications

Programming Process

1. Problem statement: The programmingprocess begins with a clear, writtenstatement of the problem to be solved by the

computer.2. Algorithm development: Once the problem

has been clearly stated and all therequirements have been understood, thenext step is to develop the program logic

necessary for accomplishing the task.*An algorithmis defined as a logical sequence

of steps that must be performed in order toaccomplish a given task.

Sample Tool:Flowchart


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Stages in the Applications

Programming Process

1. Program coding: When the programmer issatisfied with the efficacy of the logicdeveloped in the preceding step, it is time

to convert that logic (in either flowchart orpseudocode form) to the specific syntax ofthe programming language that will beused.

2. Program testing: The coded program is nextchecked for errors.

3. Program documentation: The programmingprocess is complete when the program has

been fully documented.


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Computer Programming 1

Five steps to define a programming problem:

1.Restate the problem.

2.Analyze the problem.

3. Identify the input.

4. Identify the process.

5. Identify the output.


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Common Programming Errors

1.Syntax Errors

- occur when your code violates one or more

grammar rules of C and is detected by the

compiler as it attempts to translate your

program.

Note: If a statement has a syntax error, it cannotbe translated and your program will not be

executed.


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2.Run-time Errors

- are detected errors and displayed by thecompiler during the execution of the program.

- occurs when the program directs thecomputer to perform illegal operation, such asdividing a number by zero.

- an attempt to perform an invalid operation,

detected during program execution.Note: When a run-time error occurs, the

computer will stop executing your programand will display a diagnostic message thatindicates the line where the error wasdetected.


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3. Logic Errors

- occur when a program follows a

faulty algorithm.- do not cause a run-time error anddo not display error messages, so arevery difficult to detect.

Note: The only sign of a logic error maybe incorrect program output.


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Introduction to Flowcharting


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Flowcharting

Flowchart - a graphical representationof the solution in computing aproblem in a logical and step bystep process.

- consists of geometrical symbolthat are interconnected to provide a

pictorial representation of dataprocessing.


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Algorithms and Flowcharting

Flowchart Symbols:

1. Terminal Symbol- used to designate the beginningand end of a program.

1. Input Symbol- represents an instruction to aninput device


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Flowchart Symbols:

3. Processing Symbol

- used to represent a group of programinstructions that perform a processingfunction or activity such as

mathematical operations or logicalcomparisons.

4. Output Symbol

- represents an instruction to an output

device


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Flowchart Symbols:

5. Decision Symbol

- denotes a point in the program wheremore than one path can be taken or usedto designate a decision making process.

6. Flow lines and Arrowheads

- used to show reading order or sequencein which flowchart symbols are to belead.

- show the direction of processing of dataflows.


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Flowchart Symbols:

7. On-page Connector- non processing symbol

- used to connect one part of the

flowchart to another withoutdrawing flow lines.

AA

Denotes an

entry

Denotes an

exit


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Flowchart Symbols:

8. Off-page connector- designate an exit or entry to pagewhen a flowchart requires morethan one page.

9. Preparation Symbol

- commonly used for initialization ofcounters or defining constants.


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Flowchart Symbols:

10. Predetermined Symbol- used as a subroutine symbol

- inner procedure needs to be

repeated several times.


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Introduction to the C language


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Turbo C History

Dennis Ritchie developed Turbo C atAT&T Bell Laboratories.

Turbo C was first developed forsystem programming.


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C Language Elements

The C Preprocessor- a program thatis executed before the source code is

compiled.DIRECTIVES how C preprocessorcommands are called, and begin with apound / hash symbol (#). No white

space should appear before the #, anda semi colon is NOT required at theend.


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C Language Elements

Two Common Directives:

1. #include gives program access to alibrary.

- causes the preprocessor to insertdefinitions from a standard header fileinto the program before compilation.

- tells the preprocessor that some

names used in the program are found inthe standard header file.


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C Language Elements

Two Common Directives:

2. #define allows you to make text

substitutions before compiling theprogram.

- by convention, all identifiers thatare to be changed by the

preprocessor are written in capitalletters.


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C Language Elements

#include

#define MIN 0/* #defines */

#define MAX 10

#define TRUE 1

#define FALSE 0

int main() {/* beginning of program */

int a;

int okay=FALSE;/*the compiler sees this as int okay=0;*/

while(!okay) {

printf("Input an integer between %d and %d: ", MIN,MAX); scanf("%d", &a);

if(a>MAX) {

printf("\nToo large.\n"); }

else if(a


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C Language Elements

Libraries C implementations thatcontain collections of usefulfunctions and symbols that may be

accessed by a program.

Note: A C system may expand the number ofoperation available by supplying additional

libraries. Each library has a standardheader file whose name ends with thesymbol .h.


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C Language Elements

Commenting Your CodeYou can add comments to your code by enclosing

your remarks within /* and */. However, nestedcomments aren't allowed.

A few properties of comments:They can be used to inform the person viewing thecode what the code does. This is helpful when yourevisit the code at a later date.

The compiler ignores all the comments. Hence,commenting does not affect the efficiency of the

program.You can use /* and */ to comment out sections of

code when it comes to finding errors, instead ofdeletion.


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C Language Elements

Here are examples of commented code:

/* Comments spanning several */

/* lines can be commented*/

/* out like this!*/

/* But this is a simpler way of doing it! */

// These are C++

// style comments

// and should NOT// be used with C!!

/* /* NESTED COMMENTS ARE ILLEGAL!! */ */


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C Language Elements

Function Main

Every C program has a main function. This iswhere program execution begins.

Body- the remaining line of the program inthe body.

Braces {} enclose the body of the function.

- indicates the beginning and end of thefunction main.


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C Language Elements

Two parts of the function body:

1. Declarations the part of the programthat tells the compiler the names of

memory cells in a program needed in thefunction, commonly data requirementsidentified during problem analysis.

2. Executable statements derived

statements from the algorithm intomachine language and later executed.


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C Language Elements

Your First Program

#include

int main()

{clrscr();

printf("Hello World!\n");

return 0;

getch();}


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C Language Elements

Reserved Words

In C, a reserved word is defined as

the word that has special meaning inC and cannot be used for otherpurposes.

Examples: int, void, double, return


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C Language Elements

Punctuation Marks/* */ -(slash asterisk) used to enclose a single line

remarks. -(double quotation) used to display series of

characters, and initializing string constant.; -(semicolon) statement separator, -(comma) used to separate one variable to

another= -(equal sign) used as assignment operator

-(single quotation) used for initializing character

expression& -(ampersand) used as address operator{} -(open/close braces) denotes the beginning and

end of the program.


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Variables, Data Types and Constants

Naming Conventions (Identifiers)

1. Names are made up of letters and digits.

2. The first character must be a letter.3. C is case-sensitive, example s is not

the same with S.4. The underscore symbol (_) is considered

as a letter in C. It is not recommended

to be used, however, as the firstcharacter in a name.5. At least the first 3 characters of a name

are significant.


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Names... Example

CANNOT start with a number 2i

CAN contain a number elsewhere h2o

CANNOT contain any arithmetic operators... r*s+t

CANNOT contain any other punctuation marks... #@x%!!a

CAN contain or begin with an underscore _height_

CANNOT be a C keyword struct

CANNOT contain a space im stupid

CAN be of mixed cases XSquared


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Variables- are like containers in yourcomputer's memory - you can store valuesin them and retrieve or modify them whennecessary.

- associated with a memory cell whosevalue can change as the program executes.

Variable declarationstatements thatcommunicate to the C compiler the names

of all variables used in the program and thekind of information stored in each variable.- also tells how that information will berepresented in memory.


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Syntax for Declarations:

data type variable_list;

Ex. int x,age;

float sum,a,b;

char middle_intial;


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Data Typea set of values and a setof operations that can be performedon those values.

Standard Predefined Data Type in C:

char

double

int


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Seven Basic C Data Types:

1. Text (data type char) made up of single characters(example x,#,9,E) and strings (Hello), usually 8 bits, or1 byte with the range of 0 to 255.

2. Integer values those numbers you learned to count

with.3. Floating-point values numbers that have fractional

portions such as 12.345, and exponents 1.2e+22.

4. Double-floating point values have extended range of1.7e-308 to 1.7e+308.

5. Enumerated data types allow for user-defined datatypes.

6. void signifies values that occupy 0 bit and have novalue. You can also use this type to create genericpointers.

7. Pointer does not hold information as do the other datatypes. Instead, each pointer contains the address of thememory location.


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Modifiers

The three data types above have the followingmodifiers.

short long

signed

unsigned

The modifiers define the amount of storage allocatedto the variable. The amount of storage allocatedis not cast in stone. ANSI has the following rules:

short int


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Type Bytes Bits Rangeshort int 2 16 -32,768 -> +32,767 (32kb)

unsigned short int 2 16 0 -> +65,535 (64Kb)

unsigned int 4 32 0 -> +4,294,967,295 ( 4Gb)int 4 32 -2,147,483,648 -> +2,147,483,647(2Gb)

long int 4 32 -2,147,483,648 -> +2,147,483,647(2Gb)

signed char 1 8 -128 -> +127

unsigned char 1 8 0 -> +255

float 4 32

double 8 64

long double 12 96


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Constantsidentifiers that are having aconstant value all throughout the programexecution.- also fixed values that may not be altered

by the program.

Examples:1. Character constantsenclosed between

single quotes. Ex. A, +2. Integer constantsspecified as numbers

without fractional components.Ex. 5 and -160


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Floating constantsrequire the use ofdecimal point followed by the numbersfractional components. Ex. 16.234

String constantsset of charactersenclosed by double quotes. Ex. bagand this is good

Backslash character constantsenclosing all character constants in

single quotes that works for mostprinting characters. Ex. g = \t


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SEQUENCE NAME MEANING

\a Alert Sound a beep

\b Backspace Backs up one character

\f Form feed Starts a new screen of page

\n New line Moves to the beginning of the nextline

\r CarriageReturn

Moves to the beginning of thecurrent line

\t Horizontal tab Moves to the next Tab position

\v Vertical tab Moves down a fixed amount

\\ Backslash Displays an actual backslash

\ Single quote Displays an actual single quote

\? Question mark Displays an actual question mark

\ Double quote Displays an actual double quote


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Defining Constants

#define preprocessor

- allows us to define symbolic names and

constants.A quick example:

#define PI 3.14159

This statement will translate every occurrence ofPI in the program to 3.14159.

Here is a more complete example:#define PI 3.14159 main() { int r=10; float cir;

cir = PI * (r*r); }


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Defining Constants

The const keyword.

- used to create a read only variable. Once

initialized, the value of the variable cannot bechanged but can be used just like any othervariable.

const syntax:

main()

{ const float pi = 3.14; }The const keyword is used as a qualifier to the

following data types - int float char double struct.

const int degrees = 360;

const float pi = 3.14;

const char quit = 'q';


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Operators

Assignment Operator Equal sign (=)

- the most basic operator where thevalue on the right of the equal sign

is assigned to the variable on theleft.

Example:

c = c + 1;radius = 2 * diameter;

stat = getch();


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Operators

Binary Operators

- take two operands and return a result.

Operator Use Result+ op1 + op2 adds op1 to op2

- op1 - op2 subtracts op2 from op1

* op1 * op2 multiplies op1 by op2

/ op1 / op2 divides op1 by op2% op1 % op2 computes the remainder

from dividing op1by op2


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Operators

Unary Operators

- changes the sign of a value orvariable.

- Unary minus (-) and unary plus(+)

Examples:

2 +-3

((-x) + (+y))


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Operators

Increment (++) and Decrement (--)Operators

++ increment adds one to a value of the

variable-- decrement subtracts one from a value

of the variable

Note: The value of the expression in which++ or -- operator is used depends on theposition of the operator.


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Operators

Prefix increment/decrementwhen the ++or is placed immediately in front of itsoperand. Meaning the value of theexpression is the variables value afterincrementing or decrementing.

Postfix increment/decrementwhen the++ or comes immediately after the

operand. The value of the expression isthe value of the variable before it isincremented or decremented.


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Predefined Mathematical Functions

Function Purpose

abs(x) returns the absolute value of integer x.

x=abs(-5); x=5

fabs(x) returns the absolute valued of type

double.x=fabs(-5.2); x=5.2

ceil(x) rounds up or returns the smallest wholenumber that is not less than x.

x=ceil(5.2); x=6

floor(x) rounds down or returns the largestwhole number that is not greater

than x.

x=floor(5.2); x=5


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Predefined Mathematical Functions

Function Purpose

sqrt(x) returns the non-negative square of x.

x=sqrt(25); x=5

pow(x,y) returns x to the power of y.

x=pow(4,2); x=16

sin(x) returns the sine of angle x.

cos(x) returns the cosine of angle x.

tan(x) returns the tangent of angle x.

log(x) returns the natural logarithm of x.

log10(x) returns the base 10 logarithm of x.


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Conversion Specifications

Date Types printf conversionspecification

scanf conversionspecifications

long double %Lf %Lf

double %f %lf

float %f %f

unsigned long int %lu %lu

long int %ld %ld

unsigned int %u %uint %d %d

short %hd %hd

char %c %c

String - %s


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I/O Functions

Numeric Input Command

scanf()one of the Turbo C object stream

object that is used to accept data from thestandard input, usually the keyboard.

syntax:

scanf(format, &var_name);

Example:

printf(Input side of the square:);

scanf(%d, &s);


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I/O Functions

Character/String Input Command

getche()allows the user to input acharacter and there is no need for the enter

key. Inputted char will be echoed but couldbe stored if location is specified.

Syntax:getche();var_name = getche();

Example: ans = getche();


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I/O Functions

Character/String Input Command

gets()allows the user to input a sequence

of characters (string).syntax:

gets(variable_name_of_char_type);

Example:

gets(name);


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I/O Functions

Output Command

printfwrites formatted output to the standardoutput device such as the monitor.

syntax:printf(format code,var_name);

Example:

printf(%d,x);

putswrites the string to the standard outputdevice such as the monitor and positions thecursor to the next line.

syntax:

puts(string expression);

Example: puts(CIT);


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I/O Functions

Output Command

putchar writes the single character to

the screen.syntax:

putchar(var_name);

Example:

putchar(a);


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Control Flow

Control Structures - specify the sequence ofexecution of a group of statements.

3 Types:

1. Sequential2. Conditional

3. Iterative

Sequential - organized such that statementsare executed in sequence, i.e., one afterthe other in the order of their appearancein the source code.


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Control Flow

Conditional Control Structure - organizedin such a way that there is always acondition that has to be evaluated first.The condition will either evaluate to atrue or false.

2 Types:

1. if statement (including if-else andnested if)

2. switch case statement


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Operators

Logical Operators

- used in boolean expressions and consists oflogical and", or" and not".

0-> false and 1-> true or nonzero digit

Operator Use Result&& op1 && op2 true if op1 and op2 are both

true|| op1 || op2 true if either op1 or op2 is

true

! !op1 op1 is false if its originalvalue is true and viceversa


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Control Flow

if Selection Structure

- performs an indicated action onlywhen the condition is true, otherwise

the action is skipped.

Syntax: if ()

ConditionStatementT

Example:


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p

Write a program that will allow the user to input aninteger value. If the value is greater than or equal to

zero, print the word POSITIVE.Begin

End

num

ifnum>=0

POSITIVE


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Control Flow

Other Problems:

1. Write a program that will allow the userto input a double precision floating point

value. Print the word NEGATIVE if thenumber is a negative value.

2. Write a program to input two integers.Thereafter, the program should determine

if these two numbers are equivalent. Ifthey are equivalent, print the wordEQUIVALENT.

3. Write a program that will input an integer

and determine if it is an even number.


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Control Flow

if-else Selection Structure

- allows the programmer to specify that

different actions are to be performed when

the condition is true than when thecondition is false.

- If condition evaluates to true, then

statementTis executed and statementFisskipped; otherwise, statementTis skipped

and statementFis executed.


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Control Flow

Syntax:

if (condition)

statementT;

else

statementF;

Conditio

n

StatementT

Statement

F

Example:


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Begin

End

num

POSITIVE

NEGATIVE

T

F

Write a program that accepts an integer. If the enteredinteger is positive, it prints POSITIVE. Otherwise,it prints NEGATIVE.

ifnum>=0


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Control Flow

if-else (multiple alternatives)

- The conditions in a multiple-alternativedecision are evaluated in sequence until a

truecondition is reached. If a condition istrue, the statement following it isexecuted, and the rest of the multiple-alternative decision is skipped. If a

condition is false, the statement followingit is skipped, and the condition next istested. If all conditions are false, then thestatement following the final elseisexecuted.


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T

TCondition

Statement

Condition

Condition

Statement

Statement

Statement

T

F

F

F

Control Flow

Syntax:

if (condition)

statement;

else if (condition)statement;

else if (condition)

statement;

else

statement;

Make aBegin


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program thatwould input aYEAR code(between 1and 4) andoutputFRESHMAN,

SOPHOMORE, JUNIORor SENIOR.Furthermore,

if YEAR is notbetween 1and 4, outputERROR.

End

YEAR

ifYEAR==1

ifYEAR==2

ifYEAR==3

ifYEAR==4

FRESHMAN

ERROR

SOPHOMORE

SENIOR

JUNIOR

T

T

T

T

F

F

F

F


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Control Flow

Nested-if Statement Syntax:

if (condition)

{

if(condition)

statement;

else

statement;

}

Condition

Condition

Statement

Statement

F

T

F

T


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Control Flow

Switch Statement- the controlling expression, anexpression with a value of type int or typechar, is evaluated and compared to each

of the case labels in the case constantuntil a match is found. A case constant ismade of one or more labels of the formcase followed by a constant value and acolon. When a match between the value

of the controlling expression and a caselabel value is found, the statementfollowing the case label are executed untila break statement is encountered. Thenthe rest of the switch statement isskipped.


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Control Flow

Loops and Counters

Loop a control structure that repeats agroup of steps in a program. It defines a

block of code that is repeatedly executed.Depending on the kind of loop that youare using, the block of code could beexecuted a set number of times or until a

certain condition is met.- Repetition loops can also be altered bybreak or continue statements.


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Control Flow

Break - Exits from the lowest-level loop inwhich it occurs.

- used for early exit from the loop, or forexiting a forever loop

Continue causes immediate loop iteration,skipping the rest of the loop statements

- jumps to the loop test when used withwhileor do

-jumps to loop increment, then test whenused with for

- does not exit the loop (unless next loopis false)


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Control Flow

A loop has the following components:1. Initialization of variables setting an

initial value of zero before the loopstatement is reached.

2. Condition/testing (that would evaluateto either true or false) the condition tocheck is usually made on the currentvalue of the variable initialized in (1) for itcontrols the loop repetition.

3. Body statements that are repeated inthe loop.

4. Updating a statement inside the body ofthe loop that updates the value of thevariable that is initialized during each

repetition.


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Control Flow

3 Types:

1. do-whilestatement

2.

whilestatement3. forstatement


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Control Flow

do-while statement

- This loop executes a block ofcodes as long as the specifiedcondition is true.

- It is a post checked loop becauseit checks the controlling condition

after the code is executed.


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Control Flow

Syntax:do{

statement;} while (loop repetition condition);

Example:c=1;

do{printf(Hello World\n);c++;

} while (c


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Control Flow

Initialization

Process insidethe loop

WhileCondition?

do

T

F

c=1

Whilec


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Control Flow

while Statement

- Like do-while, this will execute ablock of codes while the given

condition is true.

- It is a pre-checked loop because itchecks the controlling condition first

before the code is executed.


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Control Flow

Syntax:while (loop repetition condition){

statement;}

Example:c=1;

while (c


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Control Flow

Initialization

Process insidethe loop

WhileCondition?

T

F

c=1

Whilec


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Control Flow

for Statement

- a kind of loop command wherein theexecution of the statement does not depend on

another instruction.Syntax:

for (initialization expression; loop repetition condition;update expression)

{statement;

}


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Functions

Function a subroutine that contains one ormore statements and performs a singlewell-defined task.

2 Types:1. Pre-defined those functions written by

for us (by some other programmers).

2. User-defined those functions that we

are going to write/implement byourselves.

Difference between the main


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program and the function

Main Program

Input Output

Function

Input Output

scanf() printf() parameters return


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Functions

Begin

Calling afunction

End

Function_name (paramaters)

Return

Function body


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Functions

Function Syntax and Function Definition Syntax:

return_type function_name(parameter list){

local declaration;. . .statement/s;

}

Note: No function can have the same name asthe one of TCs reserved words.


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Functions

Where:

return_type = any standard datatype in C

parameter list consists ofvariables that receive the value ofthe arguments used in the functioncall.

Arguments a value that is passed tothe function at the time that it iscalled.


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Functions

Example:

int func(int one, int two)

{

int sum;

sum=one + two;

return sum;

}


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Functions

Functions Returning Values

The returnkeyword has two importantuses:

1. It can be used to cause an immediate exitfrom the function it is in. That is, thereturn will cause program execution toreturn to the calling as soon as it isencountered.

2. It can also be used to return a value.

Note: The returnstatement can also beused without any value associated with it.


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Functions

Function Definition (Without return typeand parameters)

Syntax:

void fname(void)

{

local declarations

executable statements

}Example:

void hello(void){

printf(Hello);

}


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Functions

Function Definition (Without return typeand with parameters)

Syntax:void fname(parameters list){

local declarationsexecutable statements

}Example:

void add(int one, int two){int sum;sum=one + two;

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