Week 1 Code Examples

hello_comp.c 
// Lecture Example
// hello_comp.c
//
// Written by: Angela Finlayson (z9801583)
// Date: 16/09/2025
//
// A program showing how to print output in C
// The first of many C programs you will C

/*
    This is another way to do comments
    in C!!!!!!!
*/

#include <stdio.h>

int main(void) {
    printf("Hello COMP1511 and COMP1911\n");
    printf("Goodbbye!!!!!!!!!!!!!\n");
    return 0;
}
hello_world.c 
// Lecture 1 Example
// hello_world.c
//
// This program was written by Angela Finlayson (z9801583)
// on 15/9/2025
//
// Our first C program

#include <stdio.h>

int main(void) {
    printf("\"Hello \\ world!\"\n");
    return 0;
}
tricky_escape.c 
// A tricky example with escape characters 
// Warning: this may hurt your brain

#include <stdio.h>

int main(void) {
    printf("\\\"\\\n");
    return 0;
}
variables_constants/print_errors.c 
// An example declaring and printing variables
// of types int, double and char
// and the kinds of errors you might make
// for COMP1511/1911 25T3
// Written by: z9801583
// Date: 16/09/2025

#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;
}
variables_constants/print_errors_original.c 
// An example declaring and printing variables
// of types int, double and char
// and the kinds of errors you might make
// for COMP1511/1911 25T3
// Written by: z9801583
// Date: 16/09/2025

#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;
}
variables_constants/print_variables.c 
// An example declaring and printing variables
// of types int, double and char
// for COMP1511/1911 25T3
// Written by: z9801583
// Date:15/9/2025

#include <stdio.h>

int main(void) {
    // Declare and initialise an int variable
    int years = 3;
     
    // Declare and initialise a double
    double lab_mark = 1.7;
   
    // Print the int and the double variable
    printf("Years: %d lab_mark %lf\n", years, lab_mark);
 
    // Declare and initialise a char variable
    char grade = 'A';

    // Print the char variable
    printf("Grade %c\n", grade);
     
    // Modify the double variable
    lab_mark = 1.719312323;
   
    // Print the double variable to 2 decimal places
    printf("%lf %.2lf\n", lab_mark, lab_mark);

    printf("%%\n");
    return 0;
}
variables_constants/scan_variables.c 
// An example declaring and printing variables
// of types int, double and char
// for COMP1511/1911 25T3
// Written by: z9801583
// Date: 16/9/2025

#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);

    // Complete
    double x;
    double y;
    printf("Please enter x and y: ");
    scanf("%lf %lf", &x, &y);
    printf("(%lf, %lf)\n",x, y);

    // What happens if the user does not type in the right thing ?
 
    return 0;
}
variables_constants/scanf_confusion.c 
#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;
}
variables_constants/scanf_magic.c 
#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;
}
variables_constants/type_troubles.c 
// 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;
}