The program below computes the product of two 3 by 3 matrices using the Pascal programming language.

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PROGRAM matrix (Input, Output); VAR A, B, C: ARRAY[1..3, 1..3] OF Integer; Arow, AColumn, Brow, BColumn, I, J, K, SUM: Integer; BEGIN Write(' ':4O, 'MATRIX MULTIPLICATION PROGRAM'); Write(' ':4O, '-----------------------------'); Writeln;} Writeln(' Enter the number of ROWS of Matrix A'); Readln(Arow); Writeln(' Enter the number of COLUMNS of Matrix A'); Readln(AColumn); Writeln(' Enter the number of ROWS of Matrix B'); Readln(Brow); Writeln(' Enter the number of COLUMNS of Matrix B'); Readln(BColumn); Writeln(); IF (AColumn = Brow) THEN BEGIN Writeln(' Enter the elements of Matrix A'); For I:= 1 to 3 DO For J:= 1 TO 3 DO Readln(A[I,J]); Writeln(' Enter the elements of Matrix B'); For I:= 1 to 3 DO For J:= 1 TO 3 DO< Readln(B[I,J]); Writeln; { Display the elements of Matrix A } Writeln(' MATRIX A'); Writeln(' --------'); For I:= 1 TO 3 DO BEGIN For J:= 1 TO 3 DO Write(A[I,J]:3); Writeln; END; Writeln; { Display the elements of Matrix B } Writeln(' MATRIX B'); Writeln(' --------'); For I:= 1 TO 3 DO BEGIN For J:= 1 TO 3 DO Write(B[I,J]:3); Writeln; END; Writeln; { Compute the Product of Matrices A and B } For I:= 1 to 3 DO For J:= 1 TO 3 DO BEGIN SUM:=0; For K:= 1 TO 3 DO SUM:= SUM + A[I,K] * B[K,J]; C[I,J]:= SUM; END; Writeln; { Display the Product of Matrices A and B } Writeln(' MATRIX AB'); Writeln(' ---------'); Writeln; For I:= 1 TO 3 DO BEGIN For J:= 1 TO 3 DO Write(C[I,J]:5); Writeln; END; END ELSE Writeln(' Matrix A and B cannot be multiplied. Enter Matrices in the order m x n and n x p'); Writeln(); Writeln(' PRESS THE ENTER KEY TO EXIT'); Readln; END. |

You can modify the program if you like. Some ideas are:

- Modify the program using Functions/Procedures.
- Modify the program such that it can compute the product for any size of two matrices provided the number of columns of first matrix is equal to the number of rows of the second matrix.

## 3 Comments

I found the difference: I was going by your image, which has 978 instead of 987 in the top row. Funny :D

Hi Tom. I just rechecked the program and got the same answer as before. You can view the screenshot here – http://goo.gl/d06oNH I guess the problem is your input. Check! In this case, when prompted to enter the elements for matrix A, type 1 then press ENTER, type 2 and press ENTER, to 9. For matrix B, type 9 then press ENTER, type 8 and press ENTER, to 1. I also solved the problem manually on paper just to make sure it was correct. Also check your code.

When I do the multiplication, I get

[30 23 19 ]

[84 65 58 ]

[138 107 97 ]

What could be going on that my calculation is close but differs from yours?