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Syntax defines the rules for structuring valid statements in C, ending with a semicolon (;).
Curly braces ({}) indicate the beginning and end of code blocks.
Semantics refers to the meaning behind syntactically correct statements and their impact on program behavior.
Control structures such as if, for, and while exemplify semantics in action, along with function calls and expressions.

Basic Data Types:
- int: Represents integer values with example int a = 5;.
- float: Represents single-precision floating-point numbers, e.g., float b = 3.14;.
- double: Represents double-precision floating-point numbers, e.g., double c = 2.71828;.
- char: Represents character values, e.g., char d = 'A';.
Derived Data Types:
- Arrays: Collections of elements of the same data type, e.g., int arr[10];.
- Structures (struct): Define a custom data type that groups different types, e.g., struct Person { char name[20]; int age; };.
- Unions: Specialized structures that allow storing different data types in the same memory location, sharing space.

Static Memory Allocation: Allocated during compile time, where the size remains constant; applicable to global and local variables.
Dynamic Memory Allocation: Handled at runtime using functions like malloc() for memory allocation and calloc() for zero-initializing memory.
realloc() allows resizing previously allocated memory, while free() deallocates memory to prevent memory leaks, which occur when allocated memory is not properly freed.

File Operations:
- fopen(): Opens a file for reading or writing.
- fscanf(), fgets(), fread(): Functions to read data from files.
- fprintf(), fputs(), fwrite(): Functions to write data to files.
- fclose(): Closes an opened file to free system resources.
File Modes:
- "r": Opens a file in read mode.
- "w": Opens or creates a file in write mode, overwriting existing content.
- "a": Opens a file in append mode to add new data at the end.
- "rb" and "wb": Open files in binary mode for reading or writing.

Pointers: Variables designed to store memory addresses, declared with syntax like int *ptr;.
Arithmetic Operations:
- Incrementing a pointer (e.g., ptr++) advances it by the size of the type it points to, allowing traversal through arrays.
- Subtracting two pointers yields the number of elements between them when both refer to the same array.
Pointers enhance the efficiency of handling arrays, strings, and dynamic memory allocation.