Objective-C-Intro

Objective-C

General-purpose programming language built on C with Smalltalk features, making it object-oriented

Objective-C Primary Use

Used for developing iOS and Mac OS X operating systems and applications

Objective-C Origin

Developed by NeXT for NeXTSTEP OS and later adopted by Apple

Objective-C Example Code

Basic program using #import, main, and NSLog to print output

Foundation Framework

Provides extended data types like NSArray, NSDictionary, NSSet and utilities for files, strings, URLs, dates, and error handling

Purpose of Learning Objective-C

To become better at designing, implementing, and maintaining systems

Objective-C Advantage

Large iOS user base and growing Mac OS X ecosystem

Try It Option Online

Allows compiling and executing Objective-C code without local setup

Local Environment Setup

Requires a text editor and GCC compiler

Text Editor

Tool for writing code (e.g., Notepad, vim, EMACS)

Source File

File containing code, usually with .m extension

GCC Compiler

Converts human-readable code into machine-executable program

Objective-C Program Structure

Consists of preprocessor commands, interface, implementation, methods, variables, statements, and comments

Preprocessor Command

#import used to include header files before compilation

Interface

Defines class structure and methods using @interface

Implementation

Defines method behavior using @implementation

Method Declaration

Defined using - (returnType)methodName;

NSObject

Base class of all Objective-C objects

Main Function

Entry point of program execution (int main())

NSLog

Function used to print output to console

Return 0

Terminates program successfully

Comments

Ignored by compiler, written using / /

Objective-C Tokens

Smallest elements of a program (keywords, identifiers, constants, strings, symbols)

Example Tokens

NSLog, @, (, "Hello, World!", )

Semicolon (;)

Terminates statements

Comments Rule

Cannot be nested and not allowed inside strings

Identifier

Name for variables, functions, etc.

Identifier Rules

Must start with letter or underscore, followed by letters/digits/underscores

Invalid Identifier Characters

@, $, %

Case Sensitivity

Manpower and manpower are different

Valid Identifiers

mohd, zara, abc, move_name, a_123, myname50, _temp, j, a23b9, retVal

Objective-C Data Types

System for declaring variables/functions that defines storage size and data interpretation

Basic Types

Arithmetic types including integer and floating-point types

Enumerated Types

Define variables with specific discrete integer values

Void Type

Indicates no value

Derived Types

Includes pointers, arrays, structures, unions, and functions

Aggregate Types

Arrays and structures

Variable

Named storage location used to store data

Variable Type Role

Determines memory size, value range, and operations

Variable Naming Rules

Letters, digits, underscore; must start with letter or underscore

Case Sensitivity (Variables)

Uppercase and lowercase are different

char

Single byte integer

int

Natural integer size of machine

float

Single precision floating-point

double

Double precision floating-point

void

No type

Variable Definition

Specifies type and allocates storage

Syntax (Definition)

type variable_list;

Example Definition

int i, j, k;

Variable Initialization

Assigning value during declaration

Example Initialization

int d = 3, f = 5;

Variable Declaration

Tells compiler variable exists without allocating memory

extern Keyword

Used to declare variables defined elsewhere

Rule

Variable can be declared many times but defined once

Lvalue

Expression that can appear on left or right side of assignment

Rvalue

Expression that can only appear on right side

Valid Example

int g = 20;

Invalid Example

10 = 20;

Constants

Fixed values that cannot change during execution

Literal

Another term for constant values

Integer Literal

Whole number constants (decimal, octal, hexadecimal)

Decimal Literal

No prefix

Octal Literal

Prefix 0

Hexadecimal Literal

Prefix 0x or 0X

Integer Literal Suffix

U (unsigned), L (long)

Valid Integer Literal

212, 215u, 0xFeeL

Invalid Integer Literal

078, 032UU

Floating Literal

Numbers with decimal/exponent

Valid Floating Literal

3.14159, 314159E-5L

Invalid Floating Literal

510E, 210f, .e55

Character Literal

Single character in single quotes

Escape Sequence

Special characters with backslash

\

Backslash

'

Single quote

"

Double quote

?

Question mark

\a

Alert/bell

\b

Backspace

\f

Form feed

\n

Newline

\r

Carriage return

\t

Horizontal tab

\v

Vertical tab

\ooo

Octal value

\xhh

Hexadecimal value

String Literal

Characters inside double quotes

String Concatenation

Adjacent strings combine automatically

#define

Preprocessor used to define constants

const Keyword

Declares typed constant

Best Practice

Constants should be in uppercase

Operator

Symbol that performs mathematical or logical operations

Types of Operators

Arithmetic, Relational, Logical, Bitwise, Assignment, Misc

+

Adds two operands (A + B = 30)

-

Subtracts second operand from first (A - B = -10)

*

Multiplies operands (A * B = 200)

/

Divides numerator by denominator (B / A = 2)

%

Modulus, returns remainder (B % A = 0)

++

Increment by 1 (A++ = 11)

--

Decrement by 1 (A-- = 9)

==

True if equal (A == B is false)