C Academy · Lesson

Implicit Conversions

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Implicit Conversions is a free C Academy lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

What Is a Conversion

When C combines values of different types, it automatically converts one to the other. This is an implicit conversion.

#include <stdio.h>
int main(void) {
    int i = 5;
    double d = i;
    printf("d = %.1f\n", d);
    return 0;
}

Integer Promotion

Small integer types like char and short are promoted to int before arithmetic.

#include <stdio.h>
int main(void) {
    char a = 10, b = 20;
    int sum = a + b;
    printf("sum = %d\n", sum);
    return 0;
}

Usual Arithmetic Conversions

In a mixed expression, the narrower operand is converted to the wider type so both match before the operation.

#include <stdio.h>
int main(void) {
    int i = 3;
    double d = 2.0;
    printf("%.1f\n", i + d);
    return 0;
}

int to double

An int assigned to a double is widened safely, keeping its exact value.

#include <stdio.h>
int main(void) {
    int count = 7;
    double avg = count;
    printf("avg = %.1f\n", avg);
    return 0;
}

double to int Truncates

Assigning a double to an int drops the fractional part. There is no rounding.

#include <stdio.h>
int main(void) {
    double d = 9.99;
    int n = d;
    printf("n = %d\n", n);
    return 0;
}

char and int

A char holds a small integer (its character code). It converts to int naturally.

#include <stdio.h>
int main(void) {
    char c = 'A';
    int code = c;
    printf("code = %d\n", code);
    return 0;
}

Conversions in Assignment

The right side is converted to the type of the left side during assignment.

#include <stdio.h>
int main(void) {
    double pi = 3;
    printf("pi = %.1f\n", pi);
    return 0;
}

Mixed Division Surprise

5 / 2 is integer division (2). Make one operand a double to get real division.

#include <stdio.h>
int main(void) {
    printf("%.1f\n", 5 / 2.0);
    return 0;
}

Bool-Like Conversions

In conditions, any nonzero value converts to true and zero to false.

#include <stdio.h>
int main(void) {
    int x = 3;
    if (x)
        printf("nonzero is true\n");
    return 0;
}

Return Value Conversion

A returned value is converted to the function return type. Returning a double from an int function truncates it.

#include <stdio.h>
int half(int n) {
    return n / 2;
}
int main(void) {
    printf("%d\n", half(7));
    return 0;
}

Passing Arguments

Arguments are converted to the parameter type when a prototype is in scope.

#include <stdio.h>
void show(double d) {
    printf("%.1f\n", d);
}
int main(void) {
    show(5);
    return 0;
}

Quick Check

Test your understanding of implicit conversions.

Recap: Implicit Conversions

You learned automatic type conversions.

C converts operands to a common type
Small ints promote to int
int to double widens safely
double to int truncates
Integer division surprises unless an operand is a double

Frequently asked questions

Is the “Implicit Conversions” lesson free?

Yes — the full text of “Implicit Conversions” is free to read here on the web, and the C Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the C Academy course, upgrade to CoddyKit PRO.

What will I learn in “Implicit Conversions”?

Automatic promotions. You practise C Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start C Academy?

No prior experience is required. C Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Implicit Conversions” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this C Academy lesson?

Yes. Every C Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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