What does a < b ? a : b print when a = 5 and b = 10?

5 — the minimum. The condition 5 < 10 is true, so the ternary selects the operand after the question mark, which is a. Flipping the comparison gives the maximum instead.

Does the C ternary operator evaluate both branches?

No. Only the branch selected by the condition is evaluated, with a sequence point after the condition — which is why expressions like p ? p->len : 0 are safe when p is NULL.

Why does the ternary print 5 and not 1 when the comparison is true?

The comparison a < b does yield 1, but the ternary uses that truth value to choose a branch — the result of the whole expression is the chosen operand (a = 5), never the comparison's 1.

Ternary Operator in C - How a < b ? a : b Picks the Minimum

Q: What does a < b ? a : b print when a = 5 and b = 10?

5 — the minimum. The condition 5 < 10 is true, so the ternary selects the operand after the question mark, which is a. Flipping the comparison gives the maximum instead.

Q: Does the C ternary operator evaluate both branches?

No. Only the branch selected by the condition is evaluated, with a sequence point after the condition — which is why expressions like p ? p->len : 0 are safe when p is NULL.

Q: Why does the ternary print 5 and not 1 when the comparison is true?

The comparison a < b does yield 1, but the ternary uses that truth value to choose a branch — the result of the whole expression is the chosen operand (a = 5), never the comparison's 1.

The ternary operator ? : is C’s only three-operand operator — a compact if/else that produces a value. The expression in this question from our C Programming Quiz App is the most famous ternary of all: the minimum idiom.

The Quiz Question

int a = 5, b = 10;
printf("%d", a < b ? a : b);

What is printed by this code?

The Correct Answer: 5

Read cond ? x : y as “if cond, then x, else y”. Here the condition a < b is true (5 < 10), so the expression evaluates to the middle operand — a, which is 5. It’s the classic minimum of two numbers one-liner. Verified on gcc 13.3 and Apple clang 21, warning-free:

$ gcc -Wall -Wextra ternary.c && ./a.out
5

Flip the comparison and you get the maximum — from the same verified run:

printf("%d\n", a < b ? a : b);   /* 5  — min  */
printf("%d\n", a > b ? a : b);   /* 10 — max  */

Why Each Wrong Answer Is Wrong

Why not 10?

10 is the else branch — chosen only when the condition is false. Picking 10 usually means reading the operands in the wrong order: the value right after ? is the “true” result, the one after : is the “false” result.

Why not 1?

1 is what would print if only the comparison a < b were passed to printf — comparisons in C yield 1 or 0, as our equality post shows. But the ternary consumes that 1 to select a branch; the 1 itself is never the result. Precedence backs this up: < binds tighter than ? :, so the expression groups as (a < b) ? a : b.

Why not 0?

0 appears nowhere: the condition is true (so not 0), and neither branch holds 0. Even if the condition were false, the result would be b = 10.

Two Properties Worth Knowing

Only one branch is evaluated. Like && and ||, the ternary is a control-flow point with a guaranteed sequence point after the condition: the not-chosen branch never runs. p ? p->len : 0 is safe on a NULL p for exactly this reason — same family of guarantees as short-circuit evaluation.

It’s an expression, not a statement. That’s its whole reason to exist — it goes where if/else can’t: inside an argument list (as in our quiz line), an initializer (int min = a < b ? a : b;), or a return. The flip side: nesting ternaries two or three deep produces famously unreadable code. Good rule — one level is idiomatic, two needs parentheses and a comment, three should be an if/else.

Frequently Asked Questions

How does the ternary operator work in C?

cond ? x : y evaluates cond; if nonzero the result is x, otherwise y. Only the selected branch is evaluated, and there’s a sequence point after the condition.

What does a < b ? a : b compute?

The minimum of a and b: when a is smaller the condition is true and a is chosen; otherwise b. Swap to a > b ? a : b for the maximum.

Does the ternary operator evaluate both branches?

No — exactly one. That makes guards like p ? p->value : default_value safe even when evaluating the other branch would crash.

Recommended Books

The C Programming Language – Kernighan & Ritchie (India) | Amazon.com
C Programming: A Modern Approach – K.N. King (India) | Amazon.com

This question is #105 in the C Programming Quiz App — 155 questions with explanations covering operators, pointers, memory, and more.
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Ternary Operator in C – How a < b ? a : b Picks the Minimum