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1. Operators
Operators in C can be categorized into several types based on their functionality:
• Arithmetic Operators:
Used for performing mathematical calculations: Addition (+), Subtraction (-), Multiplication (*), Division (/), Modulus (%)
• Relational Operators:
Used for comparing values: Equal to (==), Not equal to (!=), Greater than (>), Less than (<), Greater than or equal to (>=), Less than or equal to (<=)
• Logical Operators:
Used to combine multiple conditions: Logical AND (&&), Logical OR (||), Logical NOT (!)
• Assignment Operators:
Used to assign values to variables: Assignment (=), Addition assignment (+=), Subtraction assignment (-=), Multiplication assignment (*=), Division assignment (/=), Modulus assignment (%=)
• Increment and Decrement Operators:
Used to increase or decrease the value of a variable: Increment (++), Decrement (--)
• Bitwise Operators:
Used for manipulation of bits in integers: Bitwise AND (&), Bitwise OR (|), Bitwise XOR (^), Bitwise NOT (~), Left shift (<<), Right shift (>>)
• Ternary Operator:
Conditional operator for decision making: condition ? expression1 : expression2
2. Control Flow Statements
Control flow statements dictate the order in which statements in your code are executed based on certain conditions or loops. Key control flow statements in C include:
• Conditional Statements:
1. if statement:
2. if-else statement:
3. else-if ladder:
• Switch Statement:
Used to select one of many code blocks to be executed:
• Loops:
1. while loop:
Executes a block of code as long as a specified condition is true.
2. do-while loop:
Similar to the while loop but guarantees that the block of code is executed at least once before checking the condition.
3. for loop:
Executes a block of code a specified number of times.

1. File Handling in C
File handling in C involves operations to read from and write to files. This process typically involves the following steps:
• File Pointer:
In C, a file is accessed using a file pointer (FILE *). This pointer maintains information about the file being accessed.
• Opening a File:
Before reading from or writing to a file, you need to open it using the fopen() function:
• Reading from a File:
You can use functions like fscanf() or fgets() to read data from a file:
• Writing to a File:
Use functions like fprintf() or fputs() to write data to a file:
• Closing a File:
Always close the file using fclose() once you’re done with it to free up resources:
• Error Handling:
Check the return value of fopen() to ensure the file was opened successfully. If fp is NULL, an error occurred.
2. Error Handling in C
Error handling in C involves managing unexpected situations or errors that may occur during program execution. Common techniques include:
• Return Values:
Functions in C often return values indicating success or failure (0 for success, -1 or NULL for failure). Always check return values for errors, especially when dealing with file operations (fopen(), fclose(), etc.).
• Error Codes:
Standard library functions like errno and perror() can help diagnose errors:
• Custom Error Handling:
Use conditional statements (if, else, switch) to handle specific errors:
• Error Reporting:
Print informative error messages to stderr (fprintf(stderr, ...)):
• Cleanup:
Always clean up resources (like closing files with fclose()) before exiting due to an error to prevent resource leaks.