Linking multiple files in C - Time & Space Complexity

Time Complexity: Linking multiple files

O(1)

Understanding Time Complexity

When we link multiple files in C, the program combines code from different places. We want to see how this affects the time it takes to run.

How does adding more files change the total work the program does?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

// file1.c
int sum(int a, int b) {
    return a + b;
}

// file2.c
#include <stdio.h>
int sum(int a, int b);

int main() {
    int result = sum(5, 7);
    printf("Sum is %d\n", result);
    return 0;
}

This code shows two files: one defines a function, the other calls it. They are linked to make one program.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: The function call to sum happens once.
• How many times: Exactly one time during program run.

How Execution Grows With Input

Since the function is called once, the total work stays about the same no matter how many files we link.

Input Size (number of files)	Approx. Operations
1	1 function call
5	1 function call
10	1 function call

Pattern observation: Adding more files does not increase the number of times the function runs.

Final Time Complexity

Time Complexity: O(1)

This means the program runs in constant time because linking files does not add repeated work during execution.

Common Mistake

[X] Wrong: "More files always make the program slower because it has more code to run."

[OK] Correct: The program only runs the code it calls. Extra files add code but do not slow down execution unless their functions are used repeatedly.

Interview Connect

Understanding how linking affects program speed helps you explain how code organization impacts performance. This skill shows you think about both code structure and efficiency.

Self-Check

"What if the linked files contained functions called inside loops? How would the time complexity change?"