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CSE240 Module 3: Pointers, Arrays & Structures

CSE240 Module 3: Pointers, Arrays & Structures





CSE240 Module 3: Complete Study Guide

Pointers, Arrays, Strings & Structures in C








Quick Navigation


LO1: Pointer Basics

LO2: Arrays and Strings

LO3: Defining New Types

LO4: Contact Manager Demo

Practice Problems






LO1: Develop C Programs with Pointers


LO1.1: The Basic Concept of a Pointer

A pointer is a variable that stores the memory address of another variable. Think of it like a house address that tells you where to find something.



int x = 42; // regular variable storing value 42
int *ptr = &x; // pointer storing address of x

// Two key operators:
// & (address-of): gets the address of a variable
// * (dereference): accesses the value at an address





xValue: 42Addr: 0x1000

←
ptrValue: 0x1000Addr: 0x2000







Pointer declaration: type *name; where 'type' is what the pointer points to. The * in declaration is different from * in expressions (dereference).



LO1.2: Pointer Operators and Tracing


int a = 10, b = 20;
int *p1 = &a;
int *p2 = &b;

// Trace these operations:
*p1 = 30; // a becomes 30
p1 = p2; // p1 now points to b
*p1 = 40; // b becomes 40
a = *p2; // a becomes 40





Operation

a

b

p1 points to

p2 points to




Initial

10

20

a

b




*p1 = 30

30

20

a

b




p1 = p2

30

20

b

b




*p1 = 40

30

40

b

b




a = *p2

40

40

b

b





LO1.3: Pointers with Strings


char str[] = "Hello"; // array of characters
char *ptr = "World"; // pointer to string literal

// Key differences:
// str[] is modifiable, stored in stack
// *ptr points to read-only memory

str[0] = 'J'; // OK: now "Jello"
// ptr[0] = 'B'; // ERROR: can't modify literal

// String traversal with pointers:
char *p = str;
while (*p != '\0') {
printf("%c ", *p);
p++; // move to next character
}




String literals are stored in read-only memory.…