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Questions and Answers
What is the purpose of including a library in a C program?
What symbol is used at the end of a standard header file in C?
.h
A pair of angle brackets is used to open a predefined library.
True
What directive gives a program access to a library?
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What type of constant is represented by the value 'A'?
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How are integer constants specified?
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String constants are enclosed by single quotes.
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What is the purpose of the #define directive?
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What keyword is used for local constant declarations in C?
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The first section of a C program is called the ______.
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What is the typical return value of the main function in a C program?
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Study Notes
C Library
- C libraries are collections of functions and symbols that a program can access.
- Libraries offer several operations that programs can use.
- The standard header file for a C library ends with ".h".
- To open a predefined library, use angle brackets (<>).
- To open a user-defined library, use double quotes ("").
#include Directive
- Gives a program access to a library.
- Tells the preprocessor to insert definitions from a standard header file into the program.
- The preprocessor modifies the code before compilation.
- It also informs the preprocessor about names used in the program that are found in the standard header file.
C Constants
- These fixed values remain unchanged during program execution.
- Types of constants:
- Character constants: Enclosed in single quotes (e.g., 'A', '+').
- Integer constants: Whole numbers without fractional components (e.g., 5, -160).
- Floating constants: Numbers with decimal points followed by fractional components (e.g., 16.234).
- String constants: Sets of characters enclosed in double quotes (e.g., "bag", "this is good").
- Backslash character constants: Single-quoted character constants, used for characters that require special handling (e.g., 't' for tab).
CONSTANTS
- Constants are data values that cannot be modified during a program's execution.
- Constants have a specific type.
- Two ways to define them:
- Using the preprocessor (#define): A global declaration used to assign macro constant values.
-
Using the
constkeyword: A local declaration, usually within a function.
#define
- Allows text substitution within a program before compilation.
- Identifiers intended for preprocessor replacement are conventionally written in uppercase letters.
Using #define
- Multiple data types can be defined using #define:
- #define SCORE 100 (integer)
- #define PI 3.14159 (float)
- #define code ‘A’ (character)
- #define MSSG “Hello” (string)
Using the const keyword
- Declare constants within a function.
- Examples:
-
const char MSSG = “Hello”;(character) -
const float PI = 3.1459;(float) -
const int year = 2024;(integer) -
const code = ‘X’;(character)
-
General Structure of a C Program
- Each C program consists of two sections:
-
Heading section: Includes preprocessor directives, which typically start with
#. - Executable section: Contains the program's logic, written as code enclosed in curly braces.
-
Heading section: Includes preprocessor directives, which typically start with
- Common elements:
-
#include <stdio.h>: Includes the standard input-output library, essential for functions likeprintfandscanf. -
int main(void): The main function, the starting point of every C program. -
return 0;: Indicates successful execution of the program. - Comments: Explanatory text that is ignored by the compiler (often using
//or/* ... */).
-
Sample C Program
- Contains the
#include <stdio.h>directive for using input-output operations. - Demonstrates the
int main()function. - Includes a placeholder
printf...for potential code within the function.
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Description
This quiz covers important concepts regarding C libraries, including the use of the #include directive and different types of constants in C programming. Test your understanding of how libraries function and the significance of constants in code execution.
