Difference between revisions of "C-and-C++/C2/Tokens/English"

To define and use tokens.

We will do this with the help of an example.

We will also see some common errors and their solutions.

Ubuntu Operating system version 11.10

gcc and g++ Compiler version 4.6.1 on Ubuntu

Token is a generic word for Data types, Variables, Constants and Identifiers

I have already typed the program on the editor

So i will open it

int a = 2;

The compiler knows the meaning of keywords.

int a

int a = 2;

This is called as initialization.

The syntax for initilization is,

datatype varname = value;

varname is the name of the variable.

We can assign it a value here.

Keywords cannot be used as variable names

There are 32 keywords available in C

To name some, auto, break, case, char, const, default, enum extern, etc.

double const b = 4;

We have initialized b, by assigning a value of 4 to it.

double const b = 4;

float c

float c = 1.5;

Data type is a finite set of values along with a set of rules

char d = 'A';

Char and single quotes suggest that we are dealing with a character

As a result, d is a character variable

storing the value 'A'

a and c

a, c and d are variables

Let us now switch back to the slides and know more about constants, datatypes and variables

Constants are fixed values

They do not change during the execution of a program

There are two types of constants

Numeric constants

Character constants

It is declared as int

If we want to print an integer, we will use %d as the format specifier

Similarly, we will use float and %f for floating point numbers

For character data type, we use char and %c

For double data type, we use double and %lf.

(We CANNOT store a value in the variable above or below the range of its data type)

The value stored in the variable must not be greater or less than the range

Integer value has a

range of -32,768 to 32,767

Floating point has a range of 3.4E +/-38

Character has a range of -128 to 127

Double has a range of 1.7E +/-308

It may be used to store a data value

The values can change when a program runs

It must be declared before using a variable

We should try to give meaningful names to variables

example john, marks, sum etc.

printf("The Value of a is %d\n", a);

These cannot be used as keywords.

An identifier consists of letters and digits

Both uppercase and lowercase letters are permitted

First character must be an alphabet.

Click on Save to save the program

Let us open the terminal by pressing Ctrl, Alt and T keys simultaneously.

gcc variable.c -o var

and press Enter

./var

./tok

We can see that here we have six values after the decimal point.

And here we have only two values after the decimal point.

printf("The Value of c is %.2f", c);

It denotes that we can print only two values after the decimal point.

Come back to the terminal

execute the program

Come back to the terminal

1.500

We can see here three values after the decimal point.

Let us go back to the program.

Come back to our program

<iostream>

<iostream>

using namespace std;

cout<<

Since we use cout<< function to print a line in C++

So let us delete it

let us type \n here so again type two opening brackets

Within the double quotes type \n

Now delete this bracket.

Same way here also.

click on Save as

Save the file with .cpp extension

Come back to the terminal

g++ variable.cpp -o var

press Enter

To execute

Type

./var

Type

%d

Suppose here we type the %d in the place of %f

I will retain rest of the code as it is

Let us compile the program

format specifier ‘%d’ expects type ‘int’, but argument 2 has type ‘double’

format specifier ‘%d’ expects type ‘int’, but argument 2 has type ‘double’

Highlight

a

Here we have declared a as integer

8

Switch to the terminal

a = 8;

The new value is printed.

error

As b is an integer constant variable

It is a read only variable

We cannot change the value of b.

' '

Z is undeclared

As anything within single quotes is considered as a character value

Assignment

Write a C program to calculate the simple interest.

Hint: Simple Interest = principal * rate * time / 100

About the Spoken Tutorial Project

http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial

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Acknowledgement

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