MID$ function

The MID$ function returns a string of m characters from x$ string, beginning with the n th character.

Syntax

LN MID$ (x$,n,m)

Where,

LN : Line Number

x$  : string from which the m characters are to be extracted starting from nth character.

n   : the position from which character are to be extracted.

m  : number of character.

n must be within the range 1 to 255.

m must be within the range of 0 to 255.

if m = 0, the MID$ function returns a null string.

Examples

10 LET P$= "GOLDEN RING"

20 LET Q$= MID$(P$,2,3)

Use of MID$ function in the program.

1. CS 8.5 Display on the screen for MID$ function

Ok

LIST 

10 REM use of MID$ function

20 P$ = "GOLDEN RING"

30 Q$= MID$ (P$,2,3)

40 PRINT "Original String :-"; P$

50 PRINT "Extracted String :-" Q$

60 END

Ok

RUN

Original String :- GOLDEN RING

Extracted String :- OLD

Ok

2. CS 8.6 Display on the screen for MID$ function

Ok

10  REM Learning the use of MID$ function

20  P$= "KATHMANDU"

30  FOR I= 2 TO 3

40  FOR J= 1 TO 6

50 PRINT MID$(P$,I,J)

55 NEXT J

60 NEXT I

80 END

RUN

A

AT

ATH

ATHM

ATHMA

ATHMAN

T

TH

THM

THMA

THMAN

THMAND

Right$ function

The RIGHT$ function returns the rightmost n characters of string x$.

Syntax

LN RIGHT (x$, n)

Where ,

LN    :   Line Number

x$     :   string from which the n right most characters are to be extracted.

n       :   number of characters

• The value of n must be within the range of 0 to 255
• if n = 0, the null string (length zero) is returned.

Example

Use of RIGHT$ function in the program.

1.

CS 8.3 Display on the creen for RIGHT$ function

Ok

LIST

10 REM use of RIGHT$ function

20 P$ = "GOLDEN RING"

30 Q$ = "RIGHT$ (P$, 4)

40 PRINT " Original String - "; P$

50 PRINT " Extracted String - "; Q$

60 END

RUN

Original String - GOLDEN RING

Extracted String - RING

Ok

2..

CS 8.4 Display on the screen for RIGHT$ function

Ok

LIST 

10   REM Learning use of RIGHT$ function

20   LET A$ = "KATHMANDU"  

30   FOR I = 1 TO 9

40   Q$ = RIGHT$(A$, I)

50   PRINT Q$

60   NEXT I

70   END

Ok

RUN

U

DU

NDU

ANDU

MANDU

HMANDU

THMANDU

ATHMANDU

KATHMANDU

Ok

     

String Functions(String handling commands

String functions or string handling commands allows us to examine and modify tring and convert tring to numeric values.

• The string function with a dollar sign($) at the end returns a string whereas a string function without a dollar sign returns a numeric value.
• String operation allow combination and comparison of strings.BASIC has the following string manipulation function.

LEFT$ function

The LEFT$ function returns a string that comprises the left most n characters of x$.

Syntax

LN LEFT$*(x$,n)

Where,

LN  : Line Number

x$   : string from which n left most characters are to be returned.

n     : number of characters

• The value of n must be within range of 0 to 255.
• if n = 0, the null tring (length zero) will be returned.

Example

10 LET P$ = "GOLDEN RING"

20 LET Q$ = LEFT$(P$,9)

The LEFT$ on line 20 will return nine characters of P$ string. o Q$ will have the string.

Q$= "GOLDEN RI"

Use the LEFT$ function in the program.

(1)CS 8.1 Dissplay on the screen for LEFT$ function 

Ok

LIST

10 REM use of LEFT$ function

20 P$ = "GOLDEN RING"

30 Q$ = LEFT$(P$,6)

40 print "Original String - "; P$

50 PRINT "Extracted String  - ";Q$

60 END

Ok

RUN

Original String - GOLDEN RING

Extracted String - GOLDEN

Ok

(2)CS Display on the screen for LEFT$ function

Ok

LIST

10   REM use of LEFT$ function

20   LET A$= " KATHMANDU"

30   FOR I = 1 TO 9

40   PRINT LEFT$ (A$,I)

50  NEXT I

60  END

Ok

RUN

K

KA

KATH

KATHM

KATHMA

KATHMAN

KATHMAND

KATHMANDU

Ok

Functions and Subroutines

A function is an operation which produces a single result on some data and can be used as part of an expression. BASIC provides  a large number of utility functions which are part of BASIC language and are known as Built-in function (or Library functions). The data upon which the function acts to produce the desired result is known as argument of the function. The argument can be a variable, a constant or an expression. The argument is to be enclosed in a pair of brackets.

Example :

1. 10 PRINT ABS (X) 

2. 10 PRINT LEN ("COMPUTER")

The functions in BASIC can be divided into the following categories :

1. String function

2. Arithmetic function

3. Trigonometric function   

WHILE-WEND statement

The WHILE-WEND statement executes a series of statements in a loop as long as given condition is true.

Syntax

LN WHILE expression

.

.

.

[loop statements]

.

.

.

WEND

Where ,

LN       : Line Number

expression     : valid BASIC expression

loop statement  : Series of statement which are to be repeated

Points to Remember

• If expression is true, loop statements are executed until the WEND statement is encountered.
• If expression not true execution starts with the statement following the WEND statement.

     Example

1. Write a BASIC program to find the sum of first N numbers using WHILE-WEND loop.

CS 7.9 Display on the screen for WHILE-WEND statement.

Ok

LIST

5     REM Learning use of the WHILE....WEND statement

10   INPUT "ENTER VALUE OF N:" ; N

20   LET SUM = 0 : LET CNT = 0

30  WHILE (CNT<N)

40  CNT = CNT+1

50  SUM = SUM+CNT

60 WEND

70 PRINT " The sum of number from 1 to 100 "; N; is  : "; SUM 

80 END

Ok

RUN

ENTER VALUE OF N: : ? 100

The sum of number 1 to 100 is : 5050 

Ok