C Programming

C is a procedural programming language. It was initially developed by Dennis Ritchie as a system programming language to write an operating system. The main features of C language include low-level access to memory, simple set of keywords, and a clean style, these features make C language suitable for system programming like operating system or compiler development.

Basics:

• C Language Introduction
• C Programming Language Standard
• int (1 sign bit + 31 data bits) keyword in C
• Is it fine to write “void main()” or “main()” in C/C++?
• Difference between “int main()” and “int main(void)” in C/C++?
• Macros and Preprocessors in C
• Compiling a C program:- Behind the Scenes
• Benefits of C over other languages
• Program error signals
• Escape sequences in C
• Line Slicing in C
• C/ C++ Tokens

Variable Declaration, Definition and Scope:

• Variables and Keywords in C
• How are variables scoped in C – Static or Dynamic?
• Scope rules in C
• How Linkers Resolve Multiply Defined Global Symbols?
• Quiz on Variable Declaration and Scope
• Complicated declarations in C
• Redeclaration of global variable in C
• Internal and External Linkage
• Declare variable as constant
• Why variables doesn’t start with numbers
• Redeclaration of global variables
• Initialization of global and static variables

Data Types:

• Data Types in C
• Use of bool in C
• Integer Promotions in C
• Quiz on Data Types in C
• Comparison of a float with a value in C
• Need of long data type in C
• size_t data type in C
• Interesting facts about data-types and modifiers
• Float and Double in C
• Character arithmetic in C
• Typecasting in C

Storage Classes:

• Storage Classes in C
• Static Variables in C
• Understanding “extern” keyword in C
• What are the default values of static variables in C?
• Understanding “volatile” qualifier in C
• Const Qualifier in C
• Initialization of static variables in C
• Understanding “register” keyword in C
• Quiz on Storage Classes in C
• Understanding volatile qualifier in C- Set 1

Input/Output:

• Returned values of printf() and scanf()
• What is return type of getchar(), fgetc() and getc() ?
• Scansets in C
• puts() vs printf() for printing a string
• What is use of %n in printf() ?
• How to print % using printf()?
• Quiz on Input Output in C
• Difference between printf, sprintf and fprintf?
• Difference between getc(), getchar(), getch() and getche()
• Difference between %d and %i format specifier
• Use of fflush(stdin) in C
• Clearing input buffer in C/C++
• scanf() and fscanf() in C
• getchar_unlocked() in C
• Problem with scanf()
• Differentiate printable and control character
• rand() and srand() in C/C++

Operators:

• Introduction to operators in C and Arithmetic Operators
• Relational and Logical Operators in C
• Bitwise Operators in C
• Operator Precedence and Associativity in C
• Evaluation order of operands
• Comma in C and C++
• sizeof operator in C
• Operands for sizeof operator
• A comma operator question
• Result of comma operator as l-value in C and C++
• Order of operands for logical operators
• Increment (Decrement) operators require L-value Expression
• Precedence of postfix ++ and prefix ++ in C/C++
• Modulus on Negative Numbers
• C/C++ Ternary Operator – Some Interesting Observations
• Pre-increment (or pre-decrement) in C++
• Difference between ++*p, *p++ and *++p
• Results of comparison operations in C and C++
• To find sum of two numbers without using any operator
• Sequence Points in C
• Execution of printf with ++ operators
• Anything written in sizeof() is never executed
• Difference between strlen() and sizeof()
• Stringizing and Token-pasting operator

Preprocessor:

• Write a C macro PRINT(x) which prints x
• Variable length arguments for Macros
• Multiline macros in C
• CRASH() macro – interpretation
• The OFFSETOF() macro,
• Branch prediction macros in GCC
• Diffference between #define and const in C?
• A C Programming Language Puzzle
• What’s difference between header files “stdio.h” and “stdlib.h” ?
• How to print a variable name in C?
• Constants in C
• How a Preprocessor works
• Preprocessor Directives : Behind the scene-1
• Preprocessor Directives : Behind the scene-2
• isgraph() library function
• write your own header file in C
• difftime() library function
• tmpnam() library function
• _Generic keyword in C
• math.h library functions
• typedef versus #define in C
• strftime() library function
• exec family of functions

Arrays & Strings:

• Introduction to Arrays in C Language
• Strings in C Language
• Properties of array in C Language
• Do not use sizeof for array parameters
• Initialization of variables sized arrays in C
• Are array members deeply copied?
• What is the difference between single quoted and double quoted declaration of char array?
• Initialization of a multidimensional arrays in C/C++
• Write one line functions for strcat() and strcmp()
• What’s difference between char s[] and char *s in C
• gets() is risky to use!
• C function to Swap strings,
• Storage for Strings in C
• Difference between array and pointer
• How to dynamically allocate a 2D array in C?
• How to pass a 2D array as a parameter in C?
• How to write long strings in Multi-lines C/C++?
• What are the data types for which it is not possible to create an array?
• Variable Length Arrays in C and C++
• Short hand array notation
• Accessing array out of bounds
• strcpy() in C/C++
• strcmp() in C/C++
• strdup() and strdndup() in C/C++
• Pass an array by value
• Reverse a string in C/C++
• strpbrk() in C
• strcoll() in C/C++
• ispunct() in C
• strspn() in C
• isalpha() and isdigit() in C/C++

Control Statements:

• What should be data type of case labels of switch statement in C?
• For Versus While
• A nested loop puzzle
• switch statement in C
• Difference between while(1) and while(0)
• goto statement
• Continue Statement
• Break Statement
• Using range in switch case

Functions:

• Functions in C
• Importance of function prototype in C
• Functions that are executed before and after main() in C
• return statement vs exit() in main()
• How to Count Variable Numbers of Arguments in C?,
• What is evaluation order of function parameters in C?
• Does C support function overloading?
• How can we return multiple values from a function?
• What is the purpose of a function prototype?
• Static functions in C
• exit(), abort() and assert()
• Implicit return type int in C
• What happens when a function is called before its declaration in C?
• _Noreturn function specifier in C
• exit() vs _Exit()
• __func__ identifier in C
• Callback function in C
• Nested functions in C
• Parameter Passing Techniques
• pow() function in C
• tolower() function in C
• time() function in C

Pointers:

• Introduction to pointers in C and C++
• Double Pointer (Pointer to Pointer) in C
• Why C treats array parameters as pointers?
• Output of the program | Dereference, Reference, Dereference, Reference
• Dangling, Void , Null and Wild Pointers
• An Uncommon representation of array elements
• How to declare a pointer to a function?
• Pointer vs Array in C
• void pointer in C
• NULL pointer in C !
• Function Pointer in C
• near, far and huge pointers
• Generic Linked List in C
• restrict keyword in C
• const char *p, char * const p and const char * const p
• Pointer to an Array
• Callback function in C

Enum, Struct and Union:

• Enum in C
• Structures in C
• Union in C
• Struct Hack
• Structure Member Alignment, Padding and Data Packing
• Operations on struct variables in C
• Bit Fields in C
• Structure Sorting (By Multiple Rules) in C++
• Flexible array members in structure
• Difference between Structure and Union
• Difference between C structures and C++ structures
• Anonymous Union and Structure in C
• Compound Literals in C

Memory Management:

• Memory Layout of C Programs,
• How to deallocate memory without using free() in C?
• calloc() versus malloc()
• How does free() know the size of memory to be deallocated?
• Use of realloc()
• What is Memory Leak? How can we avoid?

File Handling:

• fseek() vs rewind() in C
• EOF, getc() and feof() in C
• fopen() for an existing file in write mode
• Read/Write structure to a file
• fgets() and gets() in C
• Basics of File Handling
• fsetpos() in C
• rename function in C/C++
• tmpfile() function in C
• fgetc() and fputc() in C
• fseek() in C/C++
• ftell() in C
• lseek() in C/C++
• remove function in C/C++
• Merge contents of two files into a third file
• Print contents of file in C

Puzzles:

• C Program to print numbers from 1 to N without using semicolon?
• How to find sum of two numbers without using any operator
• How will you show memory representation of C variables?
• Condition To Print “HelloWord”
• Change/add only one character and print ‘*’ exactly 20 times
• How can we sum the digits of a given number in single statement?
• What is the best way in C to convert a number to a string?
• Calculate Logn in one line
• Print “Even” or “Odd” without using Conditional statement
• How will you print numbers from 1 to 100 without using loop?
• How can we sum the digits of a given number in single statement?
• How will you print “Geeks for Geeks” without using a semicolon
• Write a one line C function to round floating point numbers
• How will implement Your Own sizeof
• How to count set bits in a floating point number in C?
• How to change the output of printf() in main() ?
• How to find length of a string without string.h and loop in C?
• Implement your own itoa()
• Write a C program that does not terminate when Ctrl+C is pressed
• How to measure time taken by a function in C?
• Print a long int in C using putchar() only
• Convert a floating point number to string in C
• How to write a running C code without main()?
• Write your own memcpy()
• C program to print characters without using format specifiers
• C program to print a string without any quote (singe or double) in the program
• Execute both if and else statements simultaneously
• Print “Hello World” without using any header file

Misc:

• Quine – A self-reproducing program
• Complicated declarations in C
• Use of bool in C
• Sequence Points in C | Set 1
• Optimization Techniques | Set 2 (swapping),
• ASCII NUL, ASCII 0 (’0?) and Numeric literal 0
• Little and Big Endian Mystery,
• Comparator function of qsort() in C
• Program to validate an IP address
• Multithreading in C
• Assertions in C/C++
• fork() in C
• Interesting Facts in C Programming
• Precision of floating point numbers in C++ (floor(), ceil(), trunc(), round() and setprecision())
• setjump() and longjump() in C
• nextafter() and nexttoward() in C/C++
• pthread_cancel() in C
• pthread_equal() in C
• pthread_self() in C
• Local Labels in C
• lvalue and rvalue in C
• Get and set the stack size of thread attribute
• Difference between fork() and exec()
• Errors in C/C++
• Why is C considered faster than other languages
• Incompatibilities between C and C++
• Convert C/C++ code to assembly language
• Error Handling in C
• Executing main() in C/C++ : Behind the scene
• Hygienic Macros in C
• Command line arguments in C/C++
• scanf(), fscanf(), sscanf(), scanf_s(), fscanf_s(), sscanf_s()
• Some Interesting Facts in C Programming
• Database Connectivity using C/C++
• Function Interposition in C
• Macros vs Functions
• Write your own memcpy() and memmove()