Category : Pascal Source Code
Archive   : CONVOLV.ZIP
Filename : CONVOLV.PAS

program convolv;

uses
crt;


var
lenX, lenH, lenY, code : integer;
numTerms : integer;
i,j : integer;
temp : string[10];
x,h,y : array[0..30] of real;

begin
clrscr;
writeln('This program computes the convolution of signal X(k) with');
writeln('transfer function H(k), yielding response Y(k).');
writeln;
writeln('Enter the length of the input X(k)');
readln(temp);
val(temp,lenX,code);
writeln('Enter the length of the function H(k)');
readln(temp);
val(temp,lenH,code);

{determine the length of the result}
lenY := lenX + lenH -1;
{determine the length of the table to compute values}
numTerms := lenX + 2 * (lenH-1);

{pad input array with zeroes}
for i := 0 to 30 do
x[i] := 0;
{read in input values, shifted by lenH-1}
for i := 0 to (lenX-1) do
begin
write('X(',i,') = ');
readln(temp);
val(temp,x[i+lenH-1],code);
end;

{read in transfer function}
writeln;
for i := 0 to (lenH-1) do
begin
write('H(',i,') = ');
readln(temp);
val(temp,h[i],code);
end;
writeln;

writeln('The length of the result is ',lenY);

{compute the convolution, where y(k)=SUM (x(k)*h(n-k))}
for i := 0 to (lenY-1) do
begin
y[i] := 0;
for j := 0 to (lenH-1) do
y[i] := y[i] + x[i+j]*h[lenH-1-j];
end;

writeln;
for i := 0 to (lenY-1) do
writeln('Y(',i,') = ',y[i]);

writeln('Hit to end.');
readln;
end.