C Program to Copy One Array to Another
C Program to Copy One Array to Another
A class stores five marks in their original order: 40, 35, 45, 35 and 50. The copy an array task needs a clear rule about order, duplicates and how many elements exist.
Copy each element into a separately sized destination array when the destination needs independent integer storage.
Before this exercise, review array elements and bounds and function parameters. The worked program below applies those ideas to this specific problem.
Explain
Explain why copy an array uses this sequence of operations.
Trace
Trace the sample values and predict the printed result.
Apply
Change the copied second mark to 38 and verify that the original second mark remains 35.
Copy an Array: follow the data
Given data
A class stores five marks in their original order: 40, 35, 45, 35 and 50. The copy an array task needs a clear rule about order, duplicates and how many elements exist.
Rule
Copy each element into a separately sized destination array when the destination needs independent integer storage.
Observed result
Original: 40; copy: 99
Understand the operation
An array is not assigned wholesale with copy = marks in C. This loop performs five individual assignments, then demonstrates independence by changing only the destination.
The complete example knows its five-element bound. In a reusable function, pass an explicit element count with the array pointer; a pointer alone does not report that bound. This sample has two equal marks, which makes duplicate handling observable.
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 marks[] = {40, 35, 45, 35, 50};
int count = (int)(sizeof marks / sizeof marks[0]);
int copy[5];
for (int i = 0; i < count; i++) copy[i] = marks[i];
copy[0] = 99;
printf("Original: %d; copy: %d\n", marks[0], copy[0]);
return 0;
}
Expected output
Original: 40; copy: 99
Follow the values through the code
C17 · code used in this explanation
#include <stdio.h>
int main(void) {
int marks[] = {40, 35, 45, 35, 50};
int count = (int)(sizeof marks / sizeof marks[0]);
int copy[5];
for (int i = 0; i < count; i++) copy[i] = marks[i];
copy[0] = 99;
printf("Original: %d; copy: %d\n", marks[0], copy[0]);
return 0;
}
copy receives the five current marks; replacing copy[0] does not change marks[0].
Compare the resulting output with the original sequence. A changed order and a changed set of values are different effects; decide which your operation promises.
Follow the worked calculation
Start with the sample
copy receives the five current marks; replacing copy[0] does not change marks[0].
Apply the rule
Compare the resulting output with the original sequence. A changed order and a changed set of values are different effects; decide which your operation promises.
Check the result
Original: 40; copy: 99
Original: 40; copy: 99
Try a small variation
C17 · code used in this explanation
#include <stdio.h>
int main(void) {
int marks[] = {40, 35, 45, 35, 50};
int count = (int)(sizeof marks / sizeof marks[0]);
int copy[5];
for (int i = 0; i < count; i++) copy[i] = marks[i];
copy[0] = 99;
printf("Original: %d; copy: %d\n", marks[0], copy[0]);
return 0;
}
Change the copied second mark to 38 and verify that the original second mark remains 35.
Worked answer
The complete answer keeps the five valid input elements and applies the stated alternative. Read the output against the original array rather than assume that every loop should sort, remove or overwrite values.
C17 · complete program
#include <stdio.h>
int main(void) {
int marks[] = {40, 35, 45, 35, 50};
int count = (int)(sizeof marks / sizeof marks[0]);
int copy[5];
for (int i = 0; i < count; i++) copy[i] = marks[i];
copy[1] = 38;
printf("Original: %d; copy: %d\n", marks[1], copy[1]);
return 0;
}
Expected output
Original: 35; copy: 38
Recognize the important boundaries
The destination capacity must cover every copied element. memcpy can copy representation bytes when its size and nonoverlap contracts are correct.
The sample marks and their sums fit int. General input requires both valid array bounds and an arithmetic-range contract.
Check your understanding
Choose the answer, then compare the reasoning for every option.
Use the idea independently
Copy each element into a separately sized destination array when the destination needs independent integer storage.
Continue with array indexes and bounds.
Continue with pointer and count 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.