C Program to Print a 2D Array
C Program to Print a 2D Array
A small school table has two rows and two columns. The print a 2d array operation should preserve what each row and column means, rather than treating the table as four unrelated values.
Print a two-dimensional array by traversing one complete row before moving to the next.
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 print a 2d array uses this sequence of operations.
Trace
Trace the sample values and predict the printed result.
Apply
Print column-oriented lines instead and explain how the order changes.
Print a 2D Array: follow the data
Given data
A small school table has two rows and two columns. The print a 2d array operation should preserve what each row and column means, rather than treating the table as four unrelated values.
Rule
Print a two-dimensional array by traversing one complete row before moving to the next.
Observed result
1 2 3 4
Understand the operation
The outer row index selects a row array; the inner column index selects an element inside it. A newline follows each completed row.
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}};
for (int row = 0; row < 2; row++) {
for (int col = 0; col < 2; col++) printf("%d%s", matrix[row][col], col == 1 ? "\n" : " ");
}
return 0;
}
Expected output
1 2
3 4
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}};
for (int row = 0; row < 2; row++) {
for (int col = 0; col < 2; col++) printf("%d%s", matrix[row][col], col == 1 ? "\n" : " ");
}
return 0;
}
The first row prints 1 then 2; the second prints 3 then 4.
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
The first row prints 1 then 2; the second prints 3 then 4.
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
1 2 3 4
1 2 3 4
Try a small variation
C17 · code used in this explanation
#include <stdio.h>
int main(void) {
int matrix[2][2] = {{1, 2}, {3, 4}};
for (int row = 0; row < 2; row++) {
for (int col = 0; col < 2; col++) printf("%d%s", matrix[row][col], col == 1 ? "\n" : " ");
}
return 0;
}
Print column-oriented lines instead and explain how the order changes.
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}};
for (int col = 0; col < 2; col++) {
for (int row = 0; row < 2; row++) printf("%d%s", matrix[row][col], row == 1 ? "\n" : " ");
}
return 0;
}
Expected output
1 3
2 4
Recognize the important boundaries
A fixed-column array type carries row layout into pointer arithmetic. A different column count is not interchangeable simply because the total byte count is similar.
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
Print a two-dimensional array by traversing one complete row before moving to the next.
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.