Building Blocks 2

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GW BASIC Building Blocks 2

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  • Building blocks No. 2and

    GWBASIC PROGRAMMING

  • For new comers,GWBASIC a good start-easy to learn, portable executable program with graphics capability, and is a freeware.BASIC-acronym for Beginners All-purpose Symbolic Instruction Codedesigned as a language for beginnersdeveloped by John Kemeny and Kenneth KurtzGWBASIC-version of BASIC produced by Microsoft,Inc.Other languages: FORTRAN - Formula Translation; for S and E.Gnu Fortran 77- freeware ; FORTRAN 90 is most recent version.

  • We will learn to write simple programs in GWBASICGwbasic, Fortran and other higher level languages do essentially the same thing-they interpret the program or souce code we write into a language the machine can understand.Gwbasic is a program by itself. It is an interpreter, that is, it translates our code line by line to the computer while our program is running.Fortran and similar languages interpret or compile the entire code into a machine language before the computer can run the program.

  • GETTING STARTEDBeginning a sessionGwbasic screen; KEY OFF, KEY ONCoding or writing a new program (NEW)Saving a program (SAVE or F4 key)Loading or recalling a program (LOAD or F3 key)Running a program (RUN or F2 key)Ending your computer session (SYSTEM)

  • Getting started- see how these commands work.NEWSAVE filenameLOAD filenameRUN filenameSYSTEM

    Note: close quotation optional. Extension name if not present is understood to be .BAS.

  • GWBASIC EDITORA Gwbasic pgm consists of numbered program lines: all lines are executable except REM (or ) lines. The lines are executed according to numerical sequence.Correcting errors-key operationsInserting linesSome commands for editing:CLS, FILES, LIST RENUM, DELETE

  • BUILDING BLOCKS OF A GWBASIC PROGRAM - 1A Gwbasic program as shown in the examples is made up of a structured collection of numbered LINE STATEMENTS, which are executed by the computer according to numerical sequence.Structured means the line statements carry out specific tasks in accordance with some clear and logical procedure.SYNTAXLine number statement [ : statement ] [ comment ]Note:[ ] refer to optional elements in the line statement.

  • BUILDING BLOCKS OF A GWBASIC PROGRAM - 2EXAMPLES OF LINE STATEMENTS10 X = 5 : R = 8.03 : C=A*B C is the speed in cm/sec 300 Z = 2.98*(X+1.07)500 PRINT X, Y, Z600 GOTO 19889 GOSUB 345900 LPRINT A,B,C40 IF X
  • BUILDING BLOCKS OF A GWBASIC PROGRAM - 3QUESTION: What makes up a line statement? How do we construct them?1. NUMERIC CONSTANTS - 2, 1/4, -56.083, 0.000367, -3.45E+12, 12.9213, 6.2134536789212342. VARIABLES - X , Y, DIST , A(2), B(3,4), NAME$3. OPERATIONS - arithmetic/algebraic operations: + , -, ^ , / ,\ , MOD4. RULES - naming of variables, hierarchy of operations, use of parentheses, ... 5. STRUCTURE - flow of control, program layout, ...

  • 1. NUMERIC CONSTANTS - 1TYPES OF NUMERIC CONSTANTS 1. Integer - an ordinary integer, positive or negative. Range -32768< x < 32768 . Example 7, -23, 21346, +7892. Single precision - a number with six or fewer significant digits that has a decimal point. Range 10^(-38) < x < 10^(+38) (^ refers to exponentiation, meaning raised to) Example 234.567, -9.8765, 6.023E+23

  • 1. NUMERIC CONSTANTS 2

    3. Double precision a number with seven or more significant digits and a decimal point. May have as many as 17 significant digits. Range As in single precision constants Example 3.76324523, 0.9987698543574532, 1.6578438D-12

  • 1. NUMERIC CONSTANTS - 3TYPE DECLARATION TAGSThe type of a number can be indicated by a type declaration tag: TYPE TAG EXAMPLE 1. Integer % 3%, 564% 2. Single precision ! 1.34! , 43.7865!, 23.56E-8 3. Double precision # 3.4567#, 2.67D+21

  • 2. VARIABLES - 1 RULES FOR NAMING OF VARIABLES 1. Characters must be alphanumeric,i.e., use alphabetic (A-Z) and numeral (0 9) characters only. 2. First character must be a letter. 3. Variable name may contain as many as 40 characters. No blank spaces in a name.Note: Use variable names which reflect the data stored in the variable. Also, long variable names are not practical or advisable to use in a program.

  • 2. VARIABLES - 2Variables in Gwbasic and other programming languages are classified according to the data they store. We have the following types in Gwbasic:Variable type Type declaration tag ExampleInteger% J%, KK%, ICT% Single ! X!, A7!, DIST!Double # XJ23#, AREA#String $ TITLE$, A5B$Note: String variables in Gwbasic are initialized to the null character . The other variables are initialized to 0.

  • 2. VARIABLES - 3VARIABLE DECLARATIONEach variable must be assigned a type.In general, however, it is not necessary to worry about variable type declaration in a program. Gwbasic adopts an implicit declaration of variables: variable names which end with the $ tag are declared string variables; variable names which do not end in any tag character are declared variable names of type SINGLE.Explicit variable type declaration can be accomplished using either the type declaration tags (%.!,#,$) or the DEFtype statements.

  • 2. VARIABLES - 4EXAMPLES EXPLICIT VARIABLE TYPE DECLARATIONUsing the tag characters A%, ITEM$, Y!, BBC#Using the DEFtype statements put these statements at the beginning of the program. DEFINT B-F, L-M, P This means that all variable names which begin with the letters B to F, L to M, and P are to be treated as integer variables, that is, the values they store are integer constants. DEFSNG, DEFDBL, DEFSTR statements for single, double, and string variables respectively follow the same syntax.Note: Tag characters override DEFtype statements.

  • 2. VARIABLES - 5SUBSCRIPTED VARIABLESThe purpose is to use the same variable name to refer to a collection of data or numbers.Example: X(I), I = 1, 10 A(K , L ), K = 1,10 , L = 1, 25Here , X is a one-dimensional array while A is a two- dimensional array. The dimensions or sizes of the arrays are communicated to the computer by using the DIM statement:10 DIM X(10), A(10,25)Note:Put DIM statements at the beginning of the program.

  • 3. OPERATIONS - 11. Hierarchy of operations: list is of descending priority Operation Symbol Example Exponentiation ^ 2^15, X^5, 5.12^(1/3) Multiplication, division *, / X*Y, A/2.35 Integer division \ 3\2, 9\2 Remainder in integer MOD 8 MOD 3 division Addition,subtraction +, - 6.7 +89.3 5.7

  • 3. OPERATIONS - 22. Arithmetic operations are carried out LEFT to RIGHT.3. Use parentheses whenever their use will help clarify the order of the operations that must be carried out. Inner parentheses are calculated first.Examples 3.6*89.2+6^3-8.7+2.3-1.9 ((2.8-3.5*6)/3.9)-(2.7/3.8+43.3)4. Algebraic expressions are constructed using the numeric constants,variables and the arithmetic operations discussed above. Built-in mathematical functions in Gwbasic enlarge the kind of algebraic expressions we can employ in a program.

  • BUILT-IN FUNCTIONS - 1FUNCTION SYNTAX1. Sine SIN(X) , X in radians2. Cosine COS(X)3. Tangent TAN(X)4. Arc tangent ATN(X)5. Square root SQR(X) , X >= 06. Exponential EXP(X)7. Natural logarithm LOG(X) , X > 0

  • BUILT-IN FUNCTIONS - 2FUNCTION SYNTAX8. Absolute value ABS(X)9. Greatest integer INT(X) less than or equal to X10. Remove decimal FIX(X) part of a number11. Remove the number SGN(X) but keep its sign

  • BUILT-IN FUNCTIONS - 3FUNCTION SYNTAX12. Convert X to integer constant CINT(X)13. Convert X to single precision CSNG(X) constant14. Convert X to double precision CDBL(X) constant

  • 4. RULESBy this we mean the specific procedures that we must use in order to correctly translate our code into a language the computer can understand. We have seen several of these rules. Other rules relating to the various constructs of Gwbasic may be found in the appropriate sections of the manual you downloaded from the internet.

  • 5. STRUCTUREThe structure for the various commands will be discussed when we get to them. However,the structure or layout of a Gwbasic program should look like the one below: 10 Program documentation20 Main program - dimension, type and user-defined function statements 30 Subroutines40 Data statements50 End statement

  • INPUT/OUTPUT STATEMENTS - 1The purpose of these statements is to receive data for computer processing and to output the results generated by the program.Input statements 1. INPUT - gets input data from keyboard. 100 INPUT X,Y, Z, AY$ 20 INPUT IFLAG=; IFLAG 2. READ and DATA statements come together. 50 READ X, T, N$, H 100 DATA 10.3, 25.6, argon, 234.1

  • INPUT/OUTPUT STATEMENTS - 2Output statements 1. PRINT - prints output to the screen. 100 PRINT A 50 PRINT TITLE$ 350 PRINT TAB(5);X;TAB(15);Y 2. PRINT USING - for formatting output 120 PRINT USING ##.###;A 70 PRINT USING A= ##.### J=###;A,J 3. LPRINT - as above, but print is transferred to the line printer for a hardcopy. 4. LPRINT USING - as in no. 3 above.

  • CONTROL STATEMENTS - 1There are four control statements in Gwbasic: FOR-NEXT, GOTO, IF-THEN, and IF-THEN-ELSE. 1. FOR-NEXT - for repetitive calculations. Syntax line # FOR X = X1 TO X2 [STEP X3] line # statement 1 line # statement n line # NEXT X Note: The default value of the increment X3 is 1 if the optional bracketed expression is omitted.

  • CONTROL STATEMENTS - 2 Example : FOR-NEXT statement 120 FOR J = 1 TO 50 130 K = 3*J+1 140 PRINT J =;J;TAB(12);K =;K 150 NEXT J ------------------------------------------------------------------- 20 SUM = 0. : KF%= 12 : KL% = 32 : KDEL% = 5 30 FOR K% = KF% TO KL% STEP KDEL% 40 SUM = SUM + 2.87*CSNG(K%)^3 50 NEXT K%

  • CONTROL STATEMENTS - 3Example: nested FOR-NEXT statements10 DIM A(50), B(50,20), C(50)40 FOR N = 1 TO 30 STEP 350 X = A(N)^2 + 3.87 60 FOR L = 1 TO 10 70 B(N, L) = A(N)*C(L) *X + COS(X)/LOG(X-1.05)80 NEXT L90 NEXT N

  • CONTROL STATEMENTS - 42. GOTO statement - for unconditional transfer of control Syntax line # GOTO line # Example 120 GOTO 230 70 GOTO 10

  • CONTROL STATEMENTS - 53. IF-THEN statement Relational operators Symbol Equal = Less than < Greater than > Less than or equal to = These operators are used in the argument of the IF statement to determine the flow of control.

  • CONTROL STATEMENTS - 6Compound relational operators: AND , ORSimple relational expression - involves a single relational operator: A > 12, B8) AND (C8) OR (C
  • More in the next part..