15 Top C Programming Tips to Write Smarter, Safer, and Faster Code

C Programming Tips to Improve Your Coding

We’ve put together 15 of the most impactful C programming tips and tricks in this tutorial. Whether you’re a student learning C or a working programmer, these tips are designed to be practical and useful – especially in real-world coding tasks.

Some of these insights come from deep research, and others from our hands-on coding experience. Wherever possible, we’ve focused on actual use cases and common challenges faced by C developers.

💡 Got a tip of your own? Share it in the comments! If it’s a good fit, we’ll add it to this guide – and with your permission, we’ll even credit you by tagging your LinkedIn profile. Let’s now dive into the tips, one by one.

Tip #1: Macro to Get Array Size (Any Data Type)

The following macro will help you return the size of an array of any data type.  It works by dividing the length of the array by the size of its field.

#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))

#include <stdio.h>

int main() {
    int numbers[10] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
    char *strings[5] = {"a", "b", "c", "d", "e"};

    printf("Size of numbers: %zu\n", ARRAY_SIZE(numbers));  // Output: 10
    printf("Size of strings: %zu\n", ARRAY_SIZE(strings));    // Output: 5

    return 0;
}

✅ Use this when:

• You have a fixed-size array declared on the stack.
• You want to avoid hardcoding sizes in loops or logic.

⚠️ Avoid this when:

• You’re working with pointers or dynamic arrays (malloc), as the macro won’t give correct results.

Tip #2: Measure Elapsed Execution Time

Friends, have you ever found yourself in a situation where you needed to measure the time between two occurrences? Or monitor a process that is unexpectedly consuming more time than anticipated?

Here is the code snippet to profile code performance easily with clock() from “time.h”.

#include <stdio.h>
#include <time.h>

int main() {
    clock_t start = clock();
    for (volatile int i = 0; i < 1000000; i++);
    clock_t end = clock();

    double time_taken = (double)(end - start) / CLOCKS_PER_SEC;
    printf("Time elapsed: %f seconds\n", time_taken);

    return 0;
}

✅ Portable (unlike Sleep() or windows.h)
🎯 Useful for performance testing

Tip #3: Generate Truly Random Numbers

In C programming, the stdlib.h  header provides the rand() function for generating numbers. Did you use it and realize that every time you run your program, it returns the same result?

It’s because, by default, the standard (pseudo) random number generator gets seeded with the number 1. To have it start anywhere else in the series, call the function srand (unsigned int seed).

For the seed, you can use the current time in seconds.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main() {
    srand((unsigned int)time(NULL));
    printf("Random number: %d\n", rand() % 100);  // Output: Random value 0–99

    return 0;
}

A Small Insight-
For your note, the above code seeds the generator from the current second. This fact implies that if you expect your program to re-run more than once a second, the given code may not fulfil your requirement. A possible workaround is to store the seed in a file (that you will read later from your program), and you then increment it every time the program is run.

Tip #4: Use a Decrementing Loop for Clarity

In C programming, the symbol (–>) doesn’t represent an operator. Instead, it is a combination of two separate operators, i.e., -- and > known as the “goes to.” To understand how the “goes to” operator works, go through the below code snippet.

In the example, there is conditional code that decrements variable x, while returning x’s original (not decremented) value, and then compares it with 0 using the > operator.

int x = 5;
while (x --> 0) {
    printf("%d ", x);
}

4 3 2 1 0
Press any key to continue . . .

Tip #5: Safe Input Parsing with scanf()

Find out how to handle complex inputs safely using scanf() format specifiers to avoid buffer overflows.

char a[100];
char last_name[100];

// Read characters until comma, but comma stays in input
scanf("%99[^,]", a);

// Read characters until comma, and skip the comma
scanf("%99[^,],", a);

// Read characters until newline, then skip the newline
scanf("%99[^\n]\n", a);

// Skip one word, then read next word into last_name
scanf("%*s %99s", last_name);

Practical Note: Always use width specifiers (like %99) in your format strings to prevent buffer overflows. For example, %99[^\n]\n safely reads a line without overflowing your buffer.

Tip #6: Register Cleanup Functions with atexit()

Did you know about the atexit() API? This C API registers functions that are called automatically when the program finishes its execution. This will ensure resources are freed automatically when your program exits.

#include <stdio.h>
#include <stdlib.h>

void cleanup() {
    printf("Cleaning up resources...\n");
}

int main() {
    atexit(cleanup);
    printf("Running program...\n");
    return 0;  // Output: Running program... Cleaning up resources...
}

Practical Notes:

• You can register up to 32 such functions.
• They’ll get called in the LIFO (reverse) order.
• Ideal for closing files or freeing memory.

Tip #7: Initialize Large Arrays from Files

You can easily achieve this by keeping the list values in a file. Load large datasets into arrays directly from files for cleaner code.

Create values.txt:

1.0, 2.0, 3.0

#include <stdio.h>

#define SIZE 3
double array[SIZE] = {
#include "values.txt"
};

int main() {
    for (int i = 0; i < SIZE; i++) {
        printf("%f ", array[i]);  // Output: 1.0 2.0 3.0
    }
    printf("\n");
    return 0;
}

Practical Note:

• Useful for configuration or test data
• Ensure file format matches array type to avoid any compile-time errors.

Tip #8: Perform Addition with Bitwise Operators

Bitwise operators can perform the addition (+) operation as shown in the following C code:

#include <stdio.h>

int add(int x, int y) {
    while (y != 0) {
        int carry = x & y;
        x = x ^ y;
        y = carry << 1;
    }
    return x;
}

int main() {
    printf("5 + 3 = %d\n", add(5, 3));  // Output: 8
    return 0;
}

Practical Note:

• Iterative approach saves from recursion overhead
• Use standard + for general-purpose code unless optimizing for specific hardware.

Tip #9: Swap Variables Without a Temporary Variable

Usually, to swap two numbers, you need a third one to hold a value temporarily. But you can swap without extra space.

One way is with XOR (^), which works on bits:

a = a ^ b;
b = a ^ b;
a = a ^ b;

This swaps the values without using a third variable. Another way to make this happen is by using the math:

a = a + b - (b = a);

It adds a and b, stores a in b, and subtracts to swap. But if the numbers are big, this might cause errors.

Lastly, you may try to use the XOR operator to swap two numbers. It works by applying XOR on the two values in sequence, changing their bits in a way that effectively swaps their values without needing a temporary variable.

a ^= b ^= a ^= b;

Tip #10: Safe Comparison to Prevent Assignment Errors

While matching conditions in C code, you might confuse the “=” operator with the “==” operator. This will lead to an incorrect match at runtime. To avoid this, use the defensive programming approach: write 0==x instead of x==0 so that 0=x can be caught by the compiler.

It means you should write 1==x instead of x==1 so that the compiler will always flag an error for the miswritten 1=x. So whenever you mistakenly write the following, the compiler will catch it.

#include <stdio.h>

int main() {
    int x = 0;
    if (0 == x) {  // Safe: Compiler catches `0 = x`
        printf("x is zero\n");
    }
    return 0;
}

The compiler will complain and refuse to compile the program. While it’s not possible if you are comparing two variables. For example, the expression

if (x == y)

can be incorrectly written as

if(x = y)

Tip #11: Comment Out Code Blocks Safely

Sometimes you may find yourself trying to comment out a block of code that already has some comments inside. Because C does not allow nested comments, you may find that the */ comment ends prematurely terminating your comment block. You can utilize the C Preprocessor’s #if directive to circumvent this:

#include <stdio.h>

int main() {
#if 0
    // Nested comments are safe
    printf("This is commented out\n");
#endif
    printf("Running code\n");
    return 0;
}

Tip #12: Ternary Operator for Concise Conditionals

The ternary operator is a shortcut for simple if-else conditions. Instead of writing multiple lines with an if statement, you can use it to make your code more concise and sometimes more readable when you just need to assign a value based on a condition.

For example, instead of this:

if (x < 0) {
    y = 10;
} else {
    y = 20;
}

You write like this:

y = (x < 0) ? 10 : 20;

This reduces clutter, especially when conditions are simple.

Tip #13: Understand Arrays vs. Pointers

It is easy to misunderstand the concept (especially for beginners) that pointers and arrays are the same. They are not.

• Pointers hold the memory address of another variable. Arrays are continuous blocks of memory that store elements of the same type.
• Using pointers with structs or unions, you can build data structures like linked lists or hash tables. Arrays, in contrast, hold fixed-type data in one stretch of memory.
• Pointer-based memory is usually allocated at runtime (heap). Arrays declared with fixed size are usually on the stack and set at compile time.

At compile time, an array is an array. Only during run-time, does an array devolve to a pointer.

To prove this fact, let me show you an example.

#include <stdio.h>

int main() {
    int a[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    int *p = a;
    printf("sizeof(a)=%zu, sizeof(p)=%zu\n", sizeof(a), sizeof(p));  // e.g., 40 vs 8
    return 0;
}

Tip #14: Pointer to Array vs. Array of Pointers

Many coders don’t clearly understand the difference between a pointer to an array and an array of pointers, and often mix them up.

#include <stdio.h>

int main() {
    int x[5] = {1, 2, 3, 4, 5};
    int *ptr1[5] = {&x[0], &x[1], &x[2], &x[3], &x[4]};  // Array of pointers
    int (*ptr2)[5] = &x;  // Pointer to array

    printf("ptr1[0] points to %d\n", *ptr1[0]);  // Output: 1
    printf("ptr2 points to array starting with %d\n", (*ptr2)[0]);  // Output: 1
    return 0;
}

Here, int *ptr1[5] means ptr1 is an array of 5 integer pointers (an array of int pointers).

On the other hand, int (*ptr2)[5] means ptr2 is a pointer to an array of 5 integers.

The declaration int* (ptr3[5]) is the same as ptr1 – an array of int pointers.

Tip #15: Check for Integer Overflow Safely

When doing math operations in loop or with large numbers, your code may often lead to bugs or crashes due to integer overflow. Hence, it’s a simple but important step to handle this in code to ensure calculations stay safe.

#include <stdio.h>
#include <limits.h>

int safe_add(int num1, int num2, int *sum) {
    if (num1 > INT_MAX - num2) {
        return 0;  
    }
    *sum = num1 + num2;  
    return 1;  // Success
}

int main() {
    int num1 = INT_MAX, num2 = 1, sum;

    if (safe_add(num1, num2, &sum)) {
        printf("Sum: %d\n", sum); 
    } else {
        printf("Overflow detected\n");
    }
    return 0;
}

Your Thoughts on These C Programming Tips!

Today, you explored 15 practical and impactful C programming tips that can help you write cleaner, faster, and more reliable code.

We aimed to include tips you can actually use – whether you’re coding for learning, production, or performance tuning. Many of these come from real-world experience, and we’re proud to share them with you.

This post is also a small tribute to the legendary Dennis Ritchie, the father of C.

💬 Got questions or suggestions? Drop them in the comments – we’d love to hear from you.

👇 To keep building your C/C++ skills, check out these hand-picked tutorials:

• C Programming Tutorials for Beginners
• C/C++ Programming Test for Beginners
• GDB Tips for Beginners

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Enjoy coding,
TechBeamers.