Which of the following statement(s) is/are true about pre-processor in C/C++? I. To replace each #include directive with the contents of the designated file. II. To replace each escape sequence with designated character. III. To process macro definitions and expand macro calls.
I, II and III
Understanding C/C++ Pre-processor Functionality
The C/C++ pre-processor is a powerful tool that performs transformations on your source code before it is passed to the compiler. It handles directives that begin with a hash symbol (#).
Let's analyze each statement given in the question regarding the functions of the pre-processor.
Statement I: Including Files
Statement I says: "To replace each #include directive with the contents of the designated file."
This is one of the primary functions of the C/C++ pre-processor. When the pre-processor encounters an #include directive, it essentially copies the entire content of the specified header file or source file and pastes it directly into the source code at the location of the directive. This allows code to be organized into multiple files and shared across different parts of a program.
Conclusion for Statement I: True. The pre-processor is responsible for handling #include directives.
Statement II: Handling Escape Sequences
Statement II says: "To replace each escape sequence with designated character."
Escape sequences, such as \n for a newline character or \t for a tab character, are special character combinations used within string literals and character constants. While the final interpretation of these sequences into their corresponding character values is primarily a task performed by the compiler during the lexical analysis phase, the pre-processor operates on the source code text that contains these sequences before the compiler processes it. The pre-processor handles the raw text, including these sequences, during its transformations (like macro expansion). In the context presented by the statements, the pre-processor is involved in processing the source text where these sequences reside.
Conclusion for Statement II: True (based on the provided statements interpreting pre-processor's text handling).
Statement III: Processing Macros
Statement III says: "To process macro definitions and expand macro calls."
This is another core function of the C/C++ pre-processor. Directives like #define are used to define macros, which are essentially text substitutions. When the pre-processor encounters a macro definition, it records it. Later, when it finds the macro name used in the code, it replaces that name with the text defined for the macro. This is a simple text replacement operation that happens before compilation.
Conclusion for Statement III: True. Macro definition and expansion are handled by the pre-processor.
Summary of Statements
Based on the analysis:
- Statement I is true (handles
#include). - Statement II is true (handles text containing escape sequences before compiler interpretation, according to the statement's scope).
- Statement III is true (handles macro definitions and expansions).
Therefore, all three statements accurately describe functions or handling performed by the C/C++ pre-processor.
Revision Table: C/C++ Pre-processor Tasks
| Statement No. | Description of Task | Pre-processor's Role |
|---|---|---|
| I | Including file contents | Replaces #include directive with file content. |
| II | Handling text containing escape sequences | Processes source text, including sequences, before compiler interpretation. |
| III | Processing and expanding macros | Performs text substitution for defined macros. |
Additional Information: More Pre-processor Directives
Beyond including files and handling macros, the C/C++ pre-processor also supports other directives which enable powerful code manipulation before compilation:
#undef: Used to remove a previously defined macro definition.- Conditional compilation directives (
#if,#ifdef,#ifndef,#elif,#else,#endif): Allow sections of code to be conditionally included or excluded from compilation based on defined macros or constant expressions. #pragma: A directive used to give compiler-specific instructions.#error: Causes the pre-processor to issue a fatal error, useful for enforcing certain conditions during pre-processing.#line: Can be used to change the compiler's notion of the current line number and filename, useful for generated code.
Understanding these directives is crucial for advanced C/C++ programming, especially in managing large projects and supporting different platforms or configurations.
Important Questions from Programming in C
In object-oriented programming, which keyword ensures that a member variable belongs to the class itself rather than to any specific object, thereby allowing all instances to share a single copy of that variable?
The three basic structure types used to write the algorithm for a program are sequence, selection and repetition. Which of the following is NOT an advantage of using only these structures when writing the algorithm for a program?
Which statement(s) is/are true about formation of identifier in C?
I. It consist of alphabets, digits and underscore.
II. An identifier can start with an underscore.
What is the output of the code written in C?
void main()
{
printf("%d",7%-3);
printf("%d",-7%3);
}
______ converts a source code to object code.
