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Learning is a process to acquire, enhance, or make changes in one's knowledge. Learning Module presents essential and masks non-essential pieces of knowledge. It is self paced and presents required links to important examples and related terminologies essentially required for examination centric study. The module is focused on examination system in vogue in Pakistan and helps student acquire maximum marks in limited time of study.

Sunday, April 25, 2010

Converting BASIC Programs to GW-BASIC



Converting BASIC Programs to GW-BASIC



Programs written in a BASIC language other than GW-BASIC may require some minor adjustments before they can be run. The following sections describe these adjustments.



E.1 String Dimensions


Delete all statements used to declare the length of strings. A statement such as the following:


DIM A$(I,J)

which dimensions a string array for J elements of length I, should be converted to the following statement:


DIM A$(J)

Some GW-BASIC languages use a comma or ampersand (&) for string concatenation. Each of these must be changed to a plus sign (+), which is the operator for GW-BASIC string concatenation.


In GW-BASIC, the MID$, RIGHT$, and LEFT$ functions are used to take substrings of strings. Forms such as A$(I) to access the Ith character in A$, or A$(I,J) to take a substring of A$ from position I to position J, must be changed as follows:






Other BASICGW-BASIC
X$=A$(I)X$=MID$(A$,I,1)
X$=A$(I,J)X$=MID$(A$,I,J-I+1)

If the substring reference is on the left side of an assignment, and X$ is used to replace characters in A$, convert as follows:






Other BASICGW-BASIC
A$(I)=X$MID$(A$,I,1)=X$
A$(I,J)=X$MID$(A$,I,J-I+1)=X$




E.2 Multiple Assignments


Some GW-BASIC languages allow statements of the following form to set B and C equal to zero:


10 LET B=C=0

GW-BASIC would interpret the second equal sign as a logical operator and set B equal to -1 if C equaled 0. Convert this statement to two assignment statements:


10 C=0: B=0


E.3 Multiple Statements


Some GW-BASIC languages use a backslash (\) to separate multiple statements on a line. With GW-BASIC, be sure all elements on a line are separated by a colon (:).



E.4 MAT Functions


Programs using the MAT functions available in some GW-BASIC languages must be rewritten using FOR-NEXT loops to execute properly.



E.5 FOR-NEXT Loops


Some GW-BASIC languages will always execute a FOR-NEXT loop once, regardless of the limits. GW-BASIC checks the limits first and does not execute the loop if past limits.


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