Unit 5

F1001 PROGRAMMING FUNDAMENTALS

STRUCTURE OF C PROGRAM

Basic Concepts of C Programming

Important Elements In A C Program

Data and Variables

Input and Output

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UNIT

5


INTRODUCTION

In this unit students are introduced to a simple C program. The unit describes the important elements of a

C program and the types of data that can be processed by C. It also describes C statements for performing

tasks such as getting data from the user and displaying the data on screen. Here students will be presented

with examples that illustrate many important features of C programming.

At the end of this unit, students should be able to write simple C programs in accordance to the rules and

conditions of C programming. By this time, they should know the ways to declare variables, use variables

and understand the naming conventions of variables and print outputs. Students should also have enough

knowledge to write clear, well documented and error free codes at the end of this chapter.

Basic C program structure

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NOTES

The curly braces “{ }” symbol shows the body of the program body. Any code/statements must

be written inside the body.

/* Example of basic C program Structure */

#include <stdio.h>

#define MAX 20

void main()

{

const PI = 3.142;

char letter;

int number;

huruf = ‘A’;

printf(“Enter one number : “);

scanf(“%d”, &number);

}

Comments

Header File

Main Function

Pre-processor commands

Data Type

Constant

Start of main function

Output Function

Input Function

Variable

End of main function

main() { char b;

b = ‘A’; }

(i) head

(ii) body


Comments

A line starting with /* and ending with */ is a comment.

The purpose of a comment is to document and understand the program. It can be used to tell what is

the purpose of using variables or functions. It also enables your program to be easily understood by

others.

Comment will not be executed by the compiler.

A good programming practice is to have comments in the program

Main function and functions

Every C program contains a main function which is called main()

Program execution starts from this main function.

main() function has two parts:

HEAD

Every function must have a header.

Function header is the name of that function.

main() function has a fixed name.

We cannot change the name of main() function

BODY

Every function must have a body which starts

with an open curly bracket ‘{’ and ends with a

close curly bracket ‘}’.

Every body function contains a program

statement.

A program statement will perform certain

tasks such as receiving value, display value,

calculation and so on.

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Examples :

/* this is a comment *//* This is also a comment */


Pre-processor Commands

#include <stdio.h>

# Lines starting with the ‘#’ symbol is processed by the pre-

processor, before compiling the program.

#include Is known as pre-processor directive.

Each pre-processor directive has its own header file.

Pre-processor directive gives instruction so that manipulation

can be done on the programs. Example, by instructing the

processor to include other files that are needed by the program.

<stdio.h> Used for the process of displaying output on the screen or getting

input from the user via the keyboard ( example printf and scanf)

#define AGE 22

# Lines starting with the ‘#’ symbol is processed by the pre-

processor, before compiling the program.

#define It does a search-and-replace command on a word processor (editor)

AGE Name of constant

Usually written in CAPITAL letters

22 Value assigned to AGE

Examples of Header Files in C programming

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#define <constant name> <constant value>

#include <FileName>

or


Data and Variables

HEADER FILES

LIBRARY FUNCTIONS

USES

stdio.h scanf()

printf()

gets()

getchar()

puts()

Receives input from keyboard

Displays output on screen

Receives input in the form of string Receives a character as input Displays output in string form

math.h pow(x,y)

sqrt(x)

exp(x)

Computes the value of x raised to the power of y

Computes the square root of x

Computes the exponent value of x

ctype.h isalnum(c)

isdigit(c)

ispunct(c)

islower(c)

To test whether c is alphabetic or digit

To test whether c is a numeric

To test whether c is a punctuation mark

To test whether c is a lower case character

string.h strlen(c)

strncmp(c)

strtok(c)

strncpy(c)

To get the length of a string

Compares the part of two strings

Splits string into words

Copies one part of a chosen string

conio.h clrscr() Clears the output screen

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Data

Data is an array of facts that can be modified by the computer into useful forms for human beings.

DATA

NUMERIC

Contains all types of

numbers.

Data which can be used

for calculation.

Example: sums of

money, age, and distance

(e.g: 34, 50, and 1.01).

INTEGER

All positive and negative numbers including zero and

no decimal place.

Example: 0, +1, -10.

Integers are used to represent the counting of things.

Example: Numbers of month in a year (1,2,3…)

REAL NUMBER

Contains all real numbers.

The number will be stored in floating point.

Used for metric measurement, temperature and price.

Example: 1.0, 234.55, 20.30, 36.7.

NON NUMERIC

CHARACTER

Consists of all letters, numbers and special symbols.

Characters are surrounded by single quotation mark (‘

‘).

Example: ‘A’, ‘m’,’=’, ‘#’, ‘1’ or ‘ ‘.

STRING

A combination of one or more characters.

A string is surrounded by double quotation marks (“

“).

Example: (“WELCOME TO COSMOPOINT”) or

(“8758”).

LOGICAL VALUES

Used in making yes-or-no decisions (TRUE-or-

FALSE).

Example: To check 2 integers using If…Else control

structure.

Variables

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A variable is a place to store a piece of information. Just as you might store a friend’s phone

number in your own memory.

Each variable has:

1. Name

2. Type

3. Holds a value that you assign to them

Naming Variables Must begin with a letter of the alphabet but, after the first letter,

it can contain:

1. Letters: A……Z, a……..z

2. Number : 0……9

3. Underscore character: _

Variable names are case-sensitive (example: the variable

"mYNUMBER" is different from the variable "MYNUMBER").

Cannot be more than 31 characters.

Variable names cannot be the same as the C reserved words.

Variable names cannot have spaces.

Examples : my age count 1 student 10

Variable names cannot have special characters (typographic

symbols).

Examples : ? / ~ @ + $

Valid Variables Names Examples : MyAge123, myAGE, My_Age, my_age, NAME,

Name.

Invalid Variable Names

Examples: MY AGE, 4_stu, my age, printf, 81_sales,

Aug91+Sales, Age?

Defining Variables Syntaks :

Examples : int number; float money;

Assigning Values To Variables

Syntaks :

Examples : number = 32; money = 30.50;

Data Types

Data type is the type of data that will be stored in the memory location.

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DataType VariableName;

VariableName = Expression


DATA TYPE USES EXAMPLE CODE

int int is used to define integer

numbers.

int Count;

Count = 5;

float float is used to define floating point

numbers.

float Miles;

Miles = 5.6;

double A double is used to define BIG

floating point numbers. It reserves

twice the storage for the number.

double Atoms;

Atoms= 2500000;

char A char defines characters.

char Letter;

Letter = 'x';

Variable Scope

There are two main variable scopes:

1. Local variable

2. Global variable

Local Variable

It is a variable that has been defined

immediately after the opening braces of a

Global Variable

A global variable is a variable that has been

defined before a function (usually before the

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#include <stdio.h>

FunctionName(){

int A;

/*Block of one or more */ /*C statements*/

}

Local Variable

#include <stdio.h>

char B;

FunctionName(){ int A;

/*Block of one or more */ /*C statements*/

}

Global Variable


function.

Each functions can have their own variables

declarations.

You can access (and change) local variables

only from the functions in which they are

defined. Therefore that variable's scope is

protected.

All local variables lose their definition when

their block ends.

main() function).

This means, all function in that program can

use this variable.

Global variables can be used anywhere in

the program as soon as it has been defined.

Character And String Array

Array is a list of variables or constants, and most programming languages allow the use of such lists.

A character array is the place to hold strings of information.

How to define strings data type

A string is a collection of characters to represent a name

(mother, father, student, employee, car, building, shopping

complex, software), address and extra.

Syntaks:

Example to declare character array:

char employeeName [30];

A string must be stored in character arrays, but not all

character arrays contain a string.

Contoh :

is not the same as

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char variableName [STRING_LENGTH];

string

char name[9] = "Muhammad";

char name[8] = {'M', 'u', 'h', 'a', 'm', 'm', 'a', 'd'};

Data Type

Variable Name String length Character array


Constant

The value of constant remains unchanged for the whole duration of the program execution.

Every constant has :

1. Name

2. Type

3. Values that are set to them

Syntax :

Examples :const double PI = 3.1459;#define PI 3.1459

Character Conversion

This sign % is known as conversion character in C language.

Conversion character is used to tell the input function (scanf()) and the output function (printf())

about how the data is being accepted or viewed.

Examples of usage (input function):

int a; char b; char c[5]; float d;

scanf(“%d”, &a); scanf(“%c”, &b); scanf(“%s”, c); scanf(“%f”, &d);

Examples of usage (output function) :

printf(“Integer %d”, a); printf(“Aksara Tunggal %c”, b);

printf(“Rentetan %s”, c); printf(“Titik apung %f”, d)

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%d decimal integer

%s string

%c character

%e exponential notation floating point number

%f float

%g use the short if %f or %e

%u unsigned integer

%o octal integer

%x hexadecimal integer

%% percent sign (%)

const data_type constant_name = constant_value;

or

#define constant_name constant_value


Input And Output

Input Function

Use the scanf(), gets(), getc() and

getchar() function from the stdio.h.

One of way to get input is by asking the

user to enter values into the variables using

the keyboard.

It contains conversion characters.

The conversion character explains to C

what data type to be inserted by user.

Syntax :

CC – Conversion Character

Output Function

Use the printf(), puts() and putchar()

function from stdio.h

This function sends all the output to the

screen.

Syntax :

CS: Control String – a combination of string and

conversion character

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scanf(“CC”, &variablename);

#include <stdio.h>

main(){

char name [35];

/*Input*/printf(“Enter name :”);scanf(“%s”, name);

}

printf(“CS”,variablename)printf(“CS”,variablename)

#include <stdio.h>

main (){ int age; /*Input*/ printf(“Your age ?”); scanf(“%d”, &age); /*Output*/ printf(“Your age : %d years”, age);}

Control String

Unit 5

Technology

Transcript of Unit 5