C programming: Backslash, Percentage, and Data Types

• To print a backslash, use \\
• To print a percentage sign, use %%
• \t creates a tab space
• \n creates a new line
• system("PAUSE"); prevents the program from quitting immediately, waiting for user input instead

Program Initialization

• #include <stdio.h> is included at the start of every program, allowing functions like printf and scanf to be used
• return 0; is used before ending the main program, confirming that everything ran successfully

Integer Data Types

• If an integer data type is 6-bit, it supports 64 unique combinations
• An unsigned integer can only represent non-negative values, its values range from 0 to 2ⁿ-1
• A 6-bit unsigned integer's range is 0 to 63
• A signed integer can represent both positive and negative values, its values range from -2^n-1 to 2^n-1-1
• A 6-bit signed integer's range is -32 to 31

Software Optimization

• Software speed is improved when HDD access is reduced, memory locality is maximized, and CPU computations are minimized

Character Encoding

• High voltage is not necessarily represented by "1"
• ASCII is 8 bit, and can represent 256 unique characters
• Unicode supports all of the world's languages, representing over a million unique characters

Assembly Language

• Assembly language is a technical form of high-level code, reflecting CPU operations, but is platform dependent, and not portable

Code Execution

• A bug free piece of C code execution sequence goes like this: High-level C code compiles to assembly code, which compiles into machine code

Naming conventions

• C variable and function naming rules: only letters, digits, and underscores are allow
• Variables must begin with letters and cannot contain spaces
• Keywords are not allowed (e.g., for, while, int)
• C is case sensitive

Operators

• Cannot write 100 > n > 20 in C, use logical operators && (and) || (or)
• A ternary/conditional operator is formatted as: (condition ? "if true print" : "if false print");

Switch Statements

• If break;is not added between each case of a switch statement, the code continues to execute the following cases until a break is encountered

Loops

• break; terminates the current loop
• continue; skips the current iteration of the loop and moves to the next iteration of the loop

Prime Numbers

• To determine if a number is prime, check if the number is divisible by integers from 2, to the square root of the number

Functions

• Functions do not always need to return a value in C
• do while loop executes the loop at least once, even if the condition is false
• In a function, parameters are transferred by value

Main Function

• The main function cannot be called in the program, it calls other functions within it
• All functions are not required to be called by the main function

Function Parameters

• Given long func(int n, int i) is a function, an invalid call would be func1("5", 3) because the function takes integer values
• Valid calls include func1(5,10) or long result = func1(3,2) and int result = func1(7,4)

Data Types

• The result of 5 / 2 in C is 2
• Double or long float data types can store the largest value
• The default return type of main() in C is int
• Variables defined as float use more memory than int variables
• The switch statement cannot check conditions using relational operators
• const keyword is used to define a constant variable in C
• scanf takes input from the user
• Converting a float to an int using (int) is called type casting