| Type | Description | Size | Values |
|---|---|---|---|
int | a whole number | 2-4 Bytes | -2,147,483,648 to 2,147,483,647 |
float | a number with possible decimals | 4 Bytes | 6 decimal places |
double | a number with possible decimals | 8 Bytes | 15 decimal places |
char | stores one character (letter or number) | 1 Byte | a single character |
#include <stdio.h>
int main() {
int day = 3;
printf("Hello World, today is the %drd!", day);
}| symbol | type |
|---|---|
| %d or %i | int |
| %f | double or float |
| %c | char |
It is a best practice to use all upper case letters when declaring a constant:
const int DAYSINWEEK = 7;We can cast varaibles from 1 type to another:
#include <stdio.h>
int main() {
double testScore = 95.7;
int displayScore = (int)testScore;
printf("Great work, you got a %d%% on your test\n", displayScore);
}Doing this for characters gives you the ASCII Codes:
int targetInt;
char sourceChar = 'a';
targetInt = (int)sourceChar; // 97
// similarly
int sourceInt = 65;
char targetChar;
targetChar = (char)sourceInt; // 'A'To use Booleans you have to import them since they were added in C99
#include <stdio.h>
#include <stdbool.h>
int main() {
// Create boolean variables
bool isProgrammingFun = true;
bool isFishTasty = false;
// Return boolean values
printf("%d", isProgrammingFun); // Returns 1 (true)
printf("%d", isFishTasty); // Returns 0 (false)
}if (_condition1_) {
// block of code to be executed if condition1 is true_
} else if (_condition2_) {
// block of code to be executed if the condition1 is false and condition2 is true_
} else {
// block of code to be executed if the condition1 is false and condition2 is false_
}int time = 20;
(time < 18) ? printf("Good day.") : printf("Good evening.");switch(_expression_) {
case x:
// code block_
break;
case y:
// code block_
break;
default:
// code block_
}While Loop:
int i = 0;
while (i < 5) {
printf("%d\n", i);
i++;
}Do While:
int i = 0;
do {
printf("%d\n", i);
i++;
}
while (i < 5);The break statement can also be used to jump out of a loop.
The continue statement breaks one iteration (in the loop), if a specified condition occurs, and continues with the next iteration in the loop.
int myNumbers[] = {25, 50, 75, 100};
printf("%d", myNumbers[0]);
// Outputs 25
int i;
for (i = 0; i < 4; i++) {
printf("%d\n", myNumbers[i]);
}
// Declare an array of four integers:
int myNumbers[4];
// Add elements
myNumbers[0] = 25;
myNumbers[1] = 50;
myNumbers[2] = 75;
myNumbers[3] = 100;int matrix[2][3] = { {1, 4, 2}, {3, 6, 8} };char greetings[] = "Hello World!";
printf("%s", greetings);
printf("%c", greetings[0]);You can also make a string from an array. But we have to specify a \0 a null-termiator to tell C this is the end of the string.
char greetings[] = {'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd', '!', '\0'};
printf("%s", greetings);
char greetings2[] = "Hello World!";
printf("%lu\n", sizeof(greetings)); // Outputs 13
printf("%lu\n", sizeof(greetings2)); // Outputs 13Getting the size counts the null terminator in both cases.
#include <string.h>
int main(){
char alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
printf("%d", strlen(alphabet));
return 0;
}sizeof will always give you the memory in bytes
char alphabet[50] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
printf("%d", strlen(alphabet)); // 26
printf("%d", sizeof(alphabet)); // 50char str1[20] = "Hello ";
char str2[] = "World!";
// Concatenate str2 to str1 (result is stored in str1)
strcat(str1, str2);
// Print str1
printf("%s", str1);Note that the size of str1 should be large enough to store the result of the two strings combined (20 in our example).
We can also Copy Strings:
char str1[20] = "Hello World!";
char str2[20];
// Copy str1 to str2
strcpy(str2, str1);
// Print str2
printf("%s", str2);Compare Strings
char str1[] = "Hello";
char str2[] = "Hello";
char str3[] = "Hi";
// Compare str1 and str2, and print the result
printf("%d\n", strcmp(str1, str2)); // Returns 0 (the strings are equal)
// Compare str1 and str3, and print the result
printf("%d\n", strcmp(str1, str3)); // Returns -4 (the strings are not equal)// Create an integer variable that will store the number we get from the user
int myNum;
// Ask the user to type a number
printf("Type a number: \n");
// Get and save the number the user types
scanf("%d", &myNum);
// Output the number the user typed
printf("Your number is: %d", myNum);The scanf() function takes two arguments: the format specifier of the variable (%d in the example above) and the memory address of the variable you want to store the output in.
You can take multiple inputs:
int myNum;
char myChar;
// Ask the user to type a number AND a character
printf("Type a number AND a character and press enter: \n");
// Get and save the number AND character the user types
scanf("%d %c", &myNum, &myChar);
// Print the number
printf("Your number is: %d\n", myNum);
// Print the character
printf("Your character is: %c\n", myChar);Getting strings doesn’t require an address we just need to allocate enough memory when we initalise to be able to store it
// Create a string
char firstName[30];
// Ask the user to input some text
printf("Enter your first name: \n");
// Get and save the text
scanf("%s", firstName);
// Output the text
printf("Hello %s", firstName);If your input is a string which is more than a word (split by a space) you have to use fgets
char fullName[30];
printf("Type your full name: \n");
fgets(fullName, sizeof(fullName), stdin);
printf("Hello %s", fullName);
// Type your full name: John Doe
// Hello John Doefgets() function to read a line of text. Note that you must include the following arguments: the name of the string variable, sizeof(string_name), and stdin
Use the scanf() function to get a single word as input, and use fgets() for multiple words.
The reference operator & syntax gets the address of something in memory.
int myAge = 43;
printf("%p", &myAge); // Outputs 0x7ffe5367e044Note that &myAge is often called a “pointer”. A pointer basically stores the memory address of a variable as its value. To print pointer values, we use the %p format specifier.
* syntax is used to denote a variable which holds a pointer
int myAge = 43; // An int variable
int* ptr = &myAge;If you are getting the value of a pointer you have to dereference it:
int myAge = 43; // Variable declaration
int* ptr = &myAge; // Pointer declaration
// Reference: Output the memory address of myAge with the pointer (0x7ffe5367e044)
printf("%p\n", ptr);
// Dereference: Output the value of myAge with the pointer (43)
printf("%d\n", *ptr);Define Pointer:
int* myNum; // Most used
int *myNum;
int * myNum;// Create a function
void myFunction(char name[], int age) {
printf("Hello %s. You are %d years old.\n", name, age);
}
int main() {
myFunction("Richard", 18); // call the function
return 0;
}
// Outputs "I just got executed!"Pass arrays to a function
void myFunction(int myNumbers[5]) {
for (int i = 0; i < 5; i++) {
printf("%d\n", myNumbers[i]);
}
}
int main() {
int myNumbers[5] = {10, 20, 30, 40, 50};
myFunction(myNumbers);
return 0;
}#include <math.h> // Create a structure called myStructure
struct myStructure {
int myNum;
char myLetter;
};
int main() {
// Create a structure variable of myStructure called **s1**
struct myStructure s1;
// Assign values to members of s1
s1.myNum = 13;
s1.myLetter = 'B';
// Print values
printf("My number: %d\n", s1.myNum);
printf("My letter: %c\n", s1.myLetter);
return 0;
}When assiging a value to a string in a struct you have to copy the string into that memory address
struct myStructure {
int myNum;
char myLetter;
char myString[30]; // String
};
int main() {
struct myStructure s1;
// Assign a value to the string using the strcpy function
strcpy(s1.myString, "Some text");
// Print the value
printf("My string: %s", s1.myString);
return 0;
}OR
struct myStructure {
int myNum;
char myLetter;
char myString[30];
};
int main() {
// Create a structure variable and assign values to it
struct myStructure s1 = {13, 'B', "Some text"};
// Print values
printf("%d %c %s", s1.myNum, s1.myLetter, s1.myString);
return 0;
}C has Enums too!
(pointer_name)->(variable_name)
Operation: The -> operator in C gives the value held by variable_name to structure or union variable pointer_name.
#include <stdio.h>
#include <stdlib.h>
// Creating the structure`
struct student {
char name[80];
int age;
float percentage;
};
// Creating the structure object
struct student* emp = NULL;
int main() {
// Assigning memory to struct variable emp
emp = (struct student*)
malloc (sizeof(struct student));
// Assigning value to age variable
emp->age = 18;
printf("%d", emp->age);
return 0;
}