C Program to Check Whether Two Matrices Are Equal
C Program to Check Whether Two Matrices Are Equal
A small school table has two rows and two columns. The matrix equality operation should preserve what each row and column means, rather than treating the table as four unrelated values.
Two matrices are equal when their dimensions agree and every pair of corresponding elements is equal.
Before this exercise, review array indexes and bounds and nested loops. The worked program below applies those ideas to this specific problem.
Explain
Explain why matrix equality uses this sequence of operations.
Trace
Trace the sample values and predict the printed result.
Apply
Swap the second row in the comparison matrix and explain why equal values alone do not make equal matrices.
Matrix Equality: follow the data
Given data
A small school table has two rows and two columns. The matrix equality operation should preserve what each row and column means, rather than treating the table as four unrelated values.
Rule
Two matrices are equal when their dimensions agree and every pair of corresponding elements is equal.
Observed result
Equal
Understand the operation
Compare row/column positions, not only totals or the multiset of values. Different arrangements can contain exactly the same values while representing different tables.
The example fixes both dimensions at two so every index can be checked directly. A general matrix interface must carry dimensions, require compatible shapes for its operation and validate storage for each referenced element.
Read the complete C program
The input values are written into this complete C17 example so the calculation can be reproduced without an unavailable service. Change the named data, rebuild and compare the actual output with your prediction.
C17 · complete program
#include <stdio.h>
int main(void) {
int matrix[2][2] = {{1, 2}, {3, 4}};
int other[2][2] = {{1, 2}, {3, 4}};
int equal = 1;
for (int row = 0; row < 2; row++) for (int col = 0; col < 2; col++) if (matrix[row][col] != other[row][col]) equal = 0;
puts(equal ? "Equal" : "Different");
return 0;
}
Expected output
Equal
Follow the values through the code
C17 · code used in this explanation
#include <stdio.h>
int main(void) {
int matrix[2][2] = {{1, 2}, {3, 4}};
int other[2][2] = {{1, 2}, {3, 4}};
int equal = 1;
for (int row = 0; row < 2; row++) for (int col = 0; col < 2; col++) if (matrix[row][col] != other[row][col]) equal = 0;
puts(equal ? "Equal" : "Different");
return 0;
}
All four corresponding positions match in the first fixture.
Read the resulting rows in order; moving a value to another row or column is part of the operation’s meaning, not merely an output-format choice.
Follow the worked calculation
Start with the sample
All four corresponding positions match in the first fixture.
Apply the rule
Read the resulting rows in order; moving a value to another row or column is part of the operation’s meaning, not merely an output-format choice.
Check the result
Equal
Equal
Try a small variation
C17 · code used in this explanation
#include <stdio.h>
int main(void) {
int matrix[2][2] = {{1, 2}, {3, 4}};
int other[2][2] = {{1, 2}, {3, 4}};
int equal = 1;
for (int row = 0; row < 2; row++) for (int col = 0; col < 2; col++) if (matrix[row][col] != other[row][col]) equal = 0;
puts(equal ? "Equal" : "Different");
return 0;
}
Swap the second row in the comparison matrix and explain why equal values alone do not make equal matrices.
Worked answer
The complete worked answer uses the same valid two-by-two input. Trace its index rule independently; compare each printed result with the source element or accumulation that produced it.
C17 · complete program
#include <stdio.h>
int main(void) {
int matrix[2][2] = {{1, 2}, {3, 4}};
int other[2][2] = {{1, 2}, {4, 3}};
int equal = 1;
for (int row = 0; row < 2; row++) for (int col = 0; col < 2; col++) if (matrix[row][col] != other[row][col]) equal = 0;
puts(equal ? "Equal" : "Different");
return 0;
}
Expected output
Different
Recognize the important boundaries
Dimension mismatch must be handled before element comparisons. Floating-point matrices require a domain-appropriate equality policy.
Larger or untrusted dimensions require checked storage-size calculations. Integer products and accumulated sums also need a representable-range contract.
Check your understanding
Choose the answer, then compare the reasoning for every option.
Use the idea independently
Two matrices are equal when their dimensions agree and every pair of corresponding elements is equal.
Continue with array boundaries.
Continue with function bounds contracts.
Language reference: WG14 C11 committee draft. These examples use the C17-compatible subset of the explained language features.
Reaching the recap and completing the quizzes are separate milestones.