Type Casting

Type Casting

Type casting converts a value from one type to another. C performs some conversions automatically (implicit) and allows you to request others explicitly.

Implicit Conversions

C automatically converts between compatible types when needed:

int a = 5;
long b = a;      // int -> long (safe, no data loss)
int c = 3.14;    // double -> int (truncates to 3)

Like a Changeling shapeshifting: the same underlying matter, reinterpreted as a different form.

Explicit Casts

Use the cast operator (type) to convert explicitly:

int a = 7;
int b = 2;
double result = (double)a / b;  // 3.5 (not 3)

Without the cast, 7 / 2 would be integer division (3). Casting a to double forces floating-point division.

Integer Truncation

Converting a larger type to a smaller one may lose data:

int big = 300;
char small = (char)big;  // 44 (300 % 256)

Characters and Integers

In C, char is an integer type. Every character has an ASCII value:

char c = 'A';
int ascii = c;      // 65
char next = c + 1;  // 'B' (66)

Common ASCII values:

Converting Digit Characters

char digit = '7';
int value = digit - '0';  // 7

Your Task

Write a function int to_upper(int c) that converts a lowercase letter to uppercase. If the character is not a lowercase letter, return it unchanged. Use the fact that 'a' is 97 and 'A' is 65 (a difference of 32). Print the results for 'h', 'i', '!', and 'A'.