Introduction to C
C is an imperative (procedural) language used for system programming. All code must be inside functions.
Example:
while(98) printf("#cisfun\n");
Comments
Comments in C are crucial for code documentation and clarity. They can be single-line or multi-line.
Examples:
// Single-line comment
/* Multi-line
comment */
Variables and Data Types
C supports various data types for different storage needs, such as int, char, float, double, etc.
Examples of variable declaration:
int age;
char initial;
float salary;
double pi;
Data Types | Integer types (on most 64-bit computers)
| Type | Storage size | Value range |
|---|---|---|
| char | 1 byte | -128 to 127 |
| unsigned char | 1 byte | 0 to 255 |
| short | 2 bytes | -32,768 to 32,767 |
| unsigned short | 2 bytes | 0 to 65,535 |
| int | 4 bytes | -2,147,483,648 to 2,147,483,647 |
| unsigned int | 4 bytes | 0 to 4,294,967,295 |
| long | 8 bytes | −9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 |
| unsigned long | 8 bytes | 0 to 18,446,744,073,709,551,615 |
Arrays
Arrays in C allow storing multiple elements of the same type sequentially in memory.
Example:
int numbers[10];
char name[50];
Structures
Structures in C allow defining a custom data type that groups variables under one name.
Example:
struct person {
char name[50];
int age;
};
Functions
Functions in C are blocks of code that perform a specific task. They can take parameters and return values.
Example of function definition:
int add(int a, int b) {
return a + b;
}
void greet(char *name) {
printf("Hello, %s!\n", name);
}
Control Structures
C provides control structures like if, else, while, for, etc., for decision-making and looping.
Examples:
if (condition) {
// code block
}
for (int i = 0; i < 10; i++) {
// code block
}
while (condition) {
// code block
}
Operators and Expressions
C supports various operators for arithmetic, logical, bitwise operations, etc., and expressions always evaluate to a value.
Examples:
int result = 10 + 5;
int a = 10;
int b = 5;
int sum = a + b;
if (a > b) {
// code block
}
Input and Output
In C, input and output operations are performed using functions like scanf and printf.
Example:
#include <stdio.h>
int main() {
int number;
printf("Enter a number: ");
scanf("%d", &number);
printf("You entered: %d\n", number);
return 0;
}
Pointers
Pointers in C are variables that store memory addresses. They are used for dynamic memory allocation and efficient memory management.
Example:
int num = 10;
int *ptr = #
printf("Value of num: %d\n", *ptr);
Control Flow
The flow of execution in C programs is controlled using loops and conditional statements.
Examples:
if (condition) {
// code block
}
while (condition) {
// code block
}
for (int i = 0; i < 10; i++) {
// code block
}
Function Parameters and Return Values
Functions in C can take parameters as input and return values as output.
Example:
int add(int a, int b) {
return a + b;
}
int main() {
int result = add(5, 3);
printf("Result: %d\n", result);
return 0;
}
Preprocessor Directives
Preprocessor directives in C begin with a # symbol and are used for including header files, macro definitions, etc.
Example:
#include <stdio.h>
#define PI 3.14159
int main() {
printf("Value of PI: %f\n", PI);
return 0;
}
Bitwise Operators
Bitwise operators in C perform operations at the bit-level. They are used for manipulating bits in integers.
Example:
unsigned int a = 5; // binary: 00000101
unsigned int b = 3; // binary: 00000011
unsigned int result = a & b; // bitwise AND
printf("Result: %u\n", result); // Output: 1
Typedef
The typedef keyword in C is used to create custom data type aliases for existing data types.
Example:
typedef struct {
char name[50];
int age;
} Person;
int main() {
Person p;
strcpy(p.name, "John");
p.age = 30;
printf("Name: %s, Age: %d\n", p.name, p.age);
return 0;
}
Enum
Enums in C allow defining named constants which represent integer values.
Example:
enum Day {
SUNDAY,
MONDAY,
TUESDAY,
WEDNESDAY,
THURSDAY,
FRIDAY,
SATURDAY
};
enum Day today = WEDNESDAY;
printf("Today is %d\n", today); // Output: 3 (index of WEDNESDAY)
Typedef
The typedef keyword in C is used to create custom data type aliases for existing data types.
Example:
typedef struct {
char name[50];
int age;
} Person;
int main() {
Person p;
strcpy(p.name, "John");
p.age = 30;
printf("Name: %s, Age: %d\n", p.name, p.age);
return 0;
}
Memory Management
In C, memory management involves allocating and deallocating memory using functions like malloc and free.
Example:
#include <stdio.h>
#include <stdlib.h>
int main() {
int *ptr = NULL;
ptr = (int *)malloc(5 * sizeof(int)); // Allocate memory
if (ptr == NULL) {
printf("Memory allocation failed\n");
return 1;
}
// Use allocated memory
for (int i = 0; i < 5; i++) {
ptr[i] = i * 10;
}
for (int i = 0; i < 5; i++) {
printf("%d ", ptr[i]);
}
printf("\n");
free(ptr); // Deallocate memory
return 0;
}
File Handling
C provides file handling operations to read from and write to files using FILE pointers and functions like fopen, fread, fwrite, etc.
Example:
#include <stdio.h>
int main() {
FILE *fp;
char c;
fp = fopen("file.txt", "r"); // Open file in read mode
if (fp == NULL) {
perror("Error opening file");
return -1;
}
while ((c = fgetc(fp)) != EOF) {
putchar(c); // Print each character
}
fclose(fp); // Close the file
return 0;
}
Error Handling
Error handling in C involves checking return values of functions and using techniques like errno and perror.
Example:
#include <stdio.h>
#include <errno.h>
int main() {
FILE *fp;
fp = fopen("nonexistentfile.txt", "r");
if (fp == NULL) {
perror("Error");
printf("Error code: %d\n", errno);
return 1;
}
fclose(fp);
return 0;
}
Conclusion
C is a powerful programming language known for its efficiency and versatility. Mastering C programming involves understanding its syntax, data types, control structures, functions, and more.
By practicing examples and exploring different concepts, you can become proficient in C programming and utilize it for various applications, including system programming, embedded systems, and application development.
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