In traditional C programming, if a function was declared without any explicit return type in old style code, what was the default return type assumed by the compiler?

Introduction / Context:
Earlier versions of the C programming language allowed functions to be declared without explicitly specifying a return type. In such old style code, the compiler would assume a default return type. Modern C standards discourage this practice and require explicit declarations, but understanding the historical rule remains useful for reading legacy code and for answering interview questions about language evolution. This question focuses on that default return type.

Given Data / Assumptions:

• The context is traditional or pre ANSI C, sometimes called K and R C.
• A function is written without specifying a return type before its name.
• The compiler follows the old rule instead of issuing a hard error.

Concept / Approach:
In old style C, if you wrote a function like sum(a, b) without a type before the name, the compiler implicitly treated the function as returning an int. Similarly, if a function was used before being declared, it was implicitly assumed to return int. This behaviour could lead to subtle bugs and was removed or restricted in later standards. Therefore, the correct answer must be the int type, not void or any floating point type.

Step-by-Step Solution:
Step 1: Recall the historical rule: functions without explicit type default to int.Step 2: Compare the options and identify which one matches this rule.Step 3: Option A is int, which is the type assumed in old C compilers for undeclared function return types.Step 4: Options B, C and D represent other common types but were not used as default return types.Step 5: Therefore, option A is correct for the historical default behaviour.

Verification / Alternative check:
Classic C programming books by Kernighan and Ritchie mention that int is the default type for functions and variables when no type is given. Compilers following older standards would issue warnings but still treat such functions as returning int. In contrast, modern compilers with strict standard settings reject such code. This confirms that int is the correct answer in questions that explicitly refer to default return type in old style C.

Why Other Options Are Wrong:
Option B, void, is sometimes used now for functions that do not return a value, but it must be specified explicitly; it was not used as a default. Option C, float, and option D, char, were never used as default return types; they are used only when declared. Choosing any of these would be inconsistent with the language rules described in older C standards.

Common Pitfalls:
Modern programmers, accustomed to explicit typing and strict compiler checks, may guess void as the default, thinking that absence of type means no return value. Others may not be aware of old style C at all. For exam purposes, it is important to remember that historically int was the default type, and that this rule is one reason why explicit function prototypes and types are now strongly recommended.

Final Answer:
int