# Unit 3: Programming using C/C++ (EC221) ## Basic Data Types - **int** (2 or 4 bytes), **float** (4 bytes, 6 decimals), **double** (8 bytes), **char** (1 byte), **void**; modifiers **short, long, signed, unsigned**. - C++ adds **bool** and classes; type conversion implicit and explicit (casting). ## Constants and Variables - **Variable**: named memory location whose value can change; rules: starts with a letter or underscore, no spaces or keywords, case sensitive. - **Constant**: fixed value; literals (10, 3.14, 'A', "text"), `const` keyword, `#define PI 3.14`. - Declaration: `int a = 5;` Scope: local vs global. ## Arithmetic and Logical Expressions - **Arithmetic operators**: + − * / % (modulus integer only), ++ and −−. - **Relational**: <, >, <=, >=, ==, !=. **Logical**: && (AND), || (OR), ! (NOT). **Assignment**: =, +=, −=. **Bitwise**: &, |, ^, <<, >>. - **Precedence**: brackets, unary, * / %, + −, relational, equality, &&, ||, assignment; **associativity** left to right for most. - Integer division truncates: 7/2 = 3. ## Input-Output Methods - **C**: `printf("%d", a);` and `scanf("%d", &a);`; format specifiers %d, %f, %c, %s; `getchar()`, `putchar()`, `gets()`, `puts()`; header ``. - **C++**: `cout << a;` and `cin >> a;` with `` and `using namespace std;`. ## Control Structures - **Selection**: `if`, `if-else`, **nested if**, **else-if ladder**, `switch-case` with `break` and `default`. - **Loops**: `for(init; cond; update)`, `while` (entry-controlled), `do-while` (exit-controlled, runs at least once); `break` and `continue`; **nested loops** (patterns). - Example: sum of first n numbers using a for loop. ## Procedural Abstraction (Functions) - **Function**: named block performing a task; **declaration (prototype)**, **definition**, **call**. - Syntax: `int add(int a, int b){ return a+b; }`. - **Parameter passing**: call by value; call by reference (pointers in C, references in C++). - Benefits: modularity, reuse, easy debugging; **recursion** (function calling itself, for factorial) needs a base case. - **Storage classes**: auto, static, extern, register. ## Strings and Arrays - **Array**: collection of same-type elements in contiguous memory, index from 0; `int a[5];`; one-dimensional and **two-dimensional** (matrix) arrays; initialisation `int a[3] = {1,2,3};`. - **String**: character array terminated by **'\0'**; `char s[20];` - String functions (``): `strlen()`, `strcpy()`, `strcat()`, `strcmp()`; C++ has the `string` class. ## Command Line Arguments - `int main(int argc, char *argv[])`; **argc** is the count and **argv** the array of argument strings (argv[0] is program name). - Example: `./prog 5 7`, convert with `atoi(argv[1])`. ## Basic File Handling - Declare `FILE *fp;` open with `fopen("file.txt","r")`; modes **r, w, a, r+, w+, a+**; close with `fclose(fp)`. - Functions: `fprintf`, `fscanf`, `fgets`, `fputs`, `fgetc`, `fputc`, `fread`, `fwrite`, `feof`. - C++ uses `ifstream` and `ofstream` (``). ## Error Handling - **Types of errors**: **syntax** (compile time), **logical** (wrong output), **runtime** (division by zero, file not found). - C: check return values (`fopen` returns NULL), `errno`, `perror()`, `exit()`. - C++: **exception handling** with `try`, `throw`, `catch`. - Debugging techniques: dry run, print statements, debugger. ## Likely Exam Questions 1. List the basic data types in C with sizes. (2 marks) 2. Differentiate while and do-while loops. (2 marks) 3. Write a program to find the factorial or check prime using functions. (long answer) 4. Explain arrays and strings with examples. (long answer) 5. What are command line arguments? (2 marks) 6. Explain file handling modes and functions. (long answer)