What Will I Learn?

In this tutorial, i will discuss on basic identifiers, operators and I/O statements in C program. So, by the end of this tutorial, you will be able to:

learn how to assign a correct and valid identifiers for a user data in your C program;
use valid data types and their declaration in your C program;
learn how to use assignment statements in your C program;
learn how to properly use printf and scanf function placeholder; and,
apply all this basic syntax into a simple C program t

Requirements

To be able to follow this tutorial, you should have a desktop PC or laptop installed with a Windows (7, 8, 10) operating system. You also need to install the following applications:

Software	Download Here
Code:: Blocks Open Source Cross-platform IDE	codeblocks.org
MinGW compiler	mingw.org

Difficulty

Basic

Tutorial Content

Topic 1: Assigning Valid Identifier

Variables and constant names are important so that data objects can be accessed and identified properly in a computer program. Naming all the data objects is done by the use of an identifiers.

Valid Identifiers	Invalid Identifier
address_1 , your_age, members_name, p1	3My_Address, Student-10, printf

As a general rule, valid identifier is composed of :

meaningful names that starts with an alphabet;
lower case characters;
numbers may be used with in the variable name e.g. address_1; and,
underscore ( _ ) can be used to come up with meaningful names.

Invalid identifier uses:

number at the beginning of an identifier;
mathematical operations (e.g. - , + , / , and * ); and,
reserve and library identifiers such as printf and scanf.

Topic 2: Variable Data Types and Their Declaration in C programs

Aside from constant whose values does not change in the program execution, there are data whose values changes in the program execution. This are called variable data.

Declaration of identifiers	Data definition
char char_1, char_2, char_3;	enter three character name
int year;	entered age in a year
int age_in_days	converted age in days

To declare an variable data identifier as shown from the preceding table, the basic C program syntax is "data type" (space) "identifier". For example, I want to get the age of the user; and, identify the age using the data identifier user_age. So, i will type in in the code::blocks :

int user_age;

The int signifies that for user_age contains integer. Some of the commonly used data types syntax are presented in the table below.

Type	Description	Sample Values
char	character type data	"A", "b", "!"
int	integer type(whole number) data	"300", "20", "-1"
float	float precision data	"3.14.16", ".12e+6"

Topic 3: Assignment Statements in C programs

The assignment "=" operator or the assignment statements is used to store values into a variable name.

Syntax display for Assignment Operators

Syntax	Example
result = expression	sum = a + b;

For example, you will convert age (in days) to age(in years). The assignment statement is

age_in_days=year*days_in_a_year;

which assign the value of the computation into a variable name age_in_days.

Some of the arithmetic operators

Arithmetic Operator	Meaning
+	addition
-	subtraction
*	multiplication
/	division

Topic 4: Using scanf and print f function

scanf and print if are input and ouput functions that came from <stdio.h> library file. From their name scanf inputs data from the keyboard and **printf ** outputs data on the computer screen.

Syntax display for scanf
scanf(format, input list)

scanf("%f",&user_age);

It makes the computer ask a floating point number and stores it inside the variable user_age.

scanf Placeholder	Meaning
%f	float data type
%d	integer data type
%c	single character
%c%c%c	multiple character

Example: scanf("%f%c",&user_age,&user_name);

Syntax display for printf
printf(format, print list)

Example: printf("Hi %c your age is %d,&user_name,&user_age

This is to display the input data using the scanf function discuss earlier.

Topic 5: Application of discuss topics to Code::Blocks

Now, we will create a simple program asking the user's name and age; and display the age in days.

1| Open Code:: Blocks from your desktop or from your windows menu. Click NEW PROJECT > Console application to start a new project.

2 | Go to Project in the right pane and select main.c

3 | The main.c in the code::block has an existing C program structure that includes declaration of <stdio.h> and <stdlib.h>.

4 | Now type in first the declaration of directives and constant variable to be used in this example C program that will convert age in years to days.

#include <stdio.h> #include <stdlib.h> #define days_in_years 365 int main() { char user_name1,user_name2,user_name3; float user_age; float user_age_days; printf("May I know your 3 letter nickname:"); scanf("%c%c%c", &user_name1,&user_name2,&user_name3); printf("How old are you:"); scanf("%f",&user_age); user_age_days=(user_age*days_in_years); printf("Hi %c%c%c your age is %f in days:\n",user_name1,user_name2,user_name3,user_age_days); return 0; }

From the code above lets define the elements that we have discussed earlier:

Elemets	Syntax used in the C program	Identifier/ Placeholder used	Complete code
Declaration of directives	#include	<stdio.h>, <stdlib.h>	`#include <stdio.h> #include <stdlinb.h>`
Declaration of constant variables	#define	days_in_years 365	`#define days_in_years 365`
Identifiers	char , float	user_name 1, user_name2, user_name3, user_age, user_age_days	`char user_name1,user_name2,user_name3; float user_age; float user_age_days;`
Operators	Assignment " = " operator	user_in_days	`user_in_days=user_age*days_in_years;`
I/O statements	scanf, printf	%c%c%cc , %f	`printf("May I know your 3 letter nickname:"); scanf("%c%c%c", &user_name1,&user_name2,&user_name3); printf("How old are you:"); scanf("%f",&user_age);`