Week 1 Code Examples

// A program showing how to print output in C
// The first of many C programs you will C

#include <stdio.h>

int main(void) {
    printf("Hello COMP1511 and COMP1911\n");
    return 0;
}

// A tricky example with escape characters 
// Warning: this may hurt your brain

#include <stdio.h>

int main(void) {
    printf("\\\"\\\n");
    return 0;
}

// An example declaring and printing variables
// of types int, double and char
// and the kinds of errors you might make
// for COMP1511/1911 26T3
// Written by: z9801583
// Date: 15/09/2026

#include <stdio.h>

int main(void) {
    int sides = 4;
    int result = -99;
    double value = 1.5;
    
    printf("A square has %d sides\n", sides);
    printf("The result is %d and the value is %lf\n", result, value);

    return 0;
}

// An example declaring and printing variables
// of types int, double and char
// and the kinds of errors you might make
// for COMP1511/1911 26T3
// Written by: z9801583
// Date: 15/09/2026

#include <stdio.h>

int main(void) {
    int sides;
    int result = -99;
    int value = 1.5;
    
    printf("A square has %d sides\n", sides);
    printf("The result is %d and the value is %d\n", result);

    return 0;
}

// An example declaring and printing variables
// of types int, double and char
// for COMP1511/1911 26T3
// Written by: z9801583
// Date:15/9/2026

#include <stdio.h>

int main(void) {
    // Declare a variable to store a player's initial and intialise it
    char initial = 'W';
    // Declare and initialise a variable to store an amount of gold
    int gold = 0;    
    // Declare and initialise a variable to store the health of the player
    double health = 12.5; 

    // Add code to print out the player's initial
    printf("Welcome player %c\n", initial);

    // Add code to print the gold and the health
    printf("Gold: %d Health: %.2lf\n", gold, health);
    
    return 0;
}

// An example declaring and printing variables
// of types int, double and char
// for COMP1511/1911 26T3
// Written by: z9801583
// Date: 15/9/2026

#include <stdio.h>

int main(void) {
    char initial;
    printf("Please enter your first initial: ");
    scanf("%c", &initial);

    int age;
    printf("Please enter your age: ");
    scanf("%d", &age);

    double height;
    printf("Please enter your height in cm: ");
    scanf("%lf", &height);  

    printf("Initial: %c\nAge: %d\nHeight: %lf\n", initial, age, height);

 
    return 0;
}

// An example declaring and printing variables
// of types int, double and char
// and the confusion of when scanf("%c", &initial) 
// reads in the newline character
// for COMP1511/1911 26T3
// Written by: z9801583
// Date: 15/9/2026

#include <stdio.h>


int main(void) {
    int age;
    printf("Please enter your age: ");
    scanf("%d", &age);

    double height;
    printf("Please enter your height in cm: ");
    scanf("%lf", &height);

    char initial;
    printf("Please enter your first initial: ");
    scanf("%c", &initial);

    printf("Age: %d Height: %lf Initial: %c \n", age, height, initial);
   
    return 0;
} 

// An example declaring and printing variables
// of types int
// for COMP1511/1911 26T3
// Written by: z9801583
// Date: 15/9/2026


#include <stdio.h>
int main(void) {
    int gold;
    int level;

    scanf("%d", &gold);
    scanf("%d", &level);

    printf("Gold: %d Level: %d\n", gold, level);

    // What happens if you do not type in ints?

    return 0;
}

// An example declaring and printing variables
// of types int, double and char
// and how to use scanf(" %c", &initial) 
// to skip over whitespace including the newline characters
// for COMP1511/1911 26T3
// Written by: z9801583
// Date: 15/9/2026

#include <stdio.h>


int main(void) {
    int age;
    printf("Please enter your age: ");
    scanf("%d", &age);

    double height;
    printf("Please enter your height in cm: ");
    scanf("%lf", &height);

    char initial;
    printf("Please enter your first initial: ");
    scanf(" %c", &initial);

    printf("Age: %d Height: %lf Initial: %c \n", age, height, initial);

    return 0;
} 

// A simple program demonstrating expressions
// Try to work out what will be printed without running the program


#include <stdio.h>

int main(void){
    int x = 4;
    int y = 3;
    int z = (x + y) * 10 - x;
    printf("%d\n", z);

    char c1 = 'a';
    char c2 = c1 + 1;
    printf("%c\n", c2);

    x = 3;
    y = 2;
    z = x / y;  
    printf("%d\n", z);

    x = 3;
    y = 2;
    double w = x / y;
    printf("%lf\n", w);

    return 0;
}

// Some more expressions to try
// with division and mod
// Press Ctrl / to comment and uncomment sections of code
// to see what the output would be

#include <stdio.h>

int main(void){
  
    int x = 5;
    double y = 2;
    double z = x / y;
    printf("%.1lf\n", z);

    printf("%d\n", x % 2);

    // int zero = 0;
    // printf("%d\n", x / zero);
    // printf("%d\n", x % zero);


    return 0;
}

// Some more expressions to try

#include <stdio.h>

int main(void){
    // double is not accurate
    double x = 0.3;
    printf("%lf %lf\n", x, 0.1);
    printf("%.20lf %.20lf\n", x, 0.1);
    
    // int overflow example

    int y = 2147483647; 
    printf("%d\n", y);
    y = y + 1;
    printf("%d\n", y);
    
    return 0;
}

// Write a program convert.c that 
// prompts the user enter the number of hours
// calculates how many minutes that is equivalent to
// prints out the number of minutes
// See sample output below:

// $ ./convert 
// Please enter the number of hours: 2.5
// That is 150.00 minutes

#include <stdio.h>


int main(void){
    double hours;
    double minutes;
    printf("Please enter the number of hours: ");
    scanf("%lf", &hours);

    minutes = hours * 60;
    printf("That is %.2lf minutes\n", minutes);

    return 0;
}