Tokens, Expressions and Control Structures in C++
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Hello Learners, Today in this tutorial we will learn about the Tokens, Expressions, and Control Structures in C++ with some easy and comprehensible examples. Any C++ program is written using the help of tokens, expressions, and control structures or control statements.
Tokens: The smallest individual elements of a program are known as tokens. In C and C++ most of the tokens are the same. In C++ we have the following tokens.
Keywords
Identifiers
Constants
Strings
Operators
Keywords: There are some keywords declared in C++ which are explicitly reserved identifiers and can’t be used as variable names in the program.
Identifiers: It sequence of characters that refer to the name of an array, classes, variables, a function, etc.
Example: int arr[5], here arr is the identifier for an array.Constants: A fixed value that does not change when the program is executed.
Example: 90(Integer constant), 2.2(Floating point constant), "C++"(String Constant), 'a'(Character Constant)Strings: A sequence of characters is known as strings.
Example: "India is beautiful country"Operators: Operators are used for performing various operations on variables and constants. All C operators are also applicable in C++.
Examples: Arithmetic operators('+' , '-', '*' , '/') , extraction operator(" >>"), insertion operator("<< ") etc.
#include <iostream>
#include<string>
using namespace std;
int main() {
string s1="hello world" ;
// s1 is an "identifier" of "string" data type.
cout<<s1;
// ' << ' is the insertion " operator "
const int a =100;
// Here 'a' is an " identifier "
// 'for' , 'namespace' & 'const' are " keyword "
//which can't be used as a variable name
for(int i=0 ;i<3;i++ ) {
cout << a+i << endl; // '+' is an "operator"
}
return 0;
}
Output:
hello world
100
101
102
Expressions: A combination of variables, constants, and operators arranged as per rules is called an expression. They are of seven types:
Constant Expression: It consists of only constant values.
Example: 10 , 10+20*20 , 100/20*2+221-383 etc.Integral Expression: Integral expressions are those which, after all, conversions, produce integral results.
Example: x, x *y*z , 10+int(2.0) . // Here x,y,z are integersFloat Expression: Floating expressions are those that produce floating-point results after implementing all the automatic and explicit type conversions.
Example: x+y, 5 +float(10), 22/7.0 // Here x,y are of float type.Pointer Expression: Pointer expression are those which gives the address value.
Example: &m, *ptr,*ptr+1Relational Expression: Relation expression are those that compare the two expressions and gives the bool-type result.
Example: a>b, a==b, a+b>100Logical Expression: When two or more relational expressions are combined and give the bool type result means either 0 or 1.
Example: (a<b && x==10) , (x==100 || b==2)Bitwise Expression: An expression that is used to manipulate data at a bit level. This expression is used for shifting or testing of bits.
Example: a >> 5 // Shift 5 bit position to right a << 2 // Shift 2 bit position to left
Control Structures: Several statements by which we can control the flow of execution or behaviour of a program. C++ has three kinds of control structures.
Sequence Structure: When a set of program statements is executed sequentially then it is a sequence structure.
Selection Structure: A set of program statements executed based on whether a boolean condition is true or false.
Loop Structure: A set of program statements executed until the loop condition is met.
Here is an example of Sequence Structure
#include <iostream>
using namespace std;
int main() {
int a=10;
int b=20;
int total;
std::cout << "Statements are executed sequentially in sequence structure" << std::endl;
total=a+b;
std::cout << total << std::endl;
return 0;
}
Output:
Statements are executed sequentially in sequence structure
30
Here are the examples of Selection Structure
#include <iostream>
using namespace std;
int main() {
int a=1000, b=100;
if(a<b){
std::cout << "a is less than b" << std::endl;
} else if(a>b) {
std::cout << "a is greater than b" << std::endl;
} else {
std::cout << "a is equal to b" << std::endl;
}
return 0;
}
Output:
a is greater than b
#include <iostream>
using namespace std;
int main() {
int a=1000 , b=100 ,c=10,d;
cout<<"Press 1 to print value of a \n Press 2 to print value of b \n Press 3 to print value of c \n ";
cin>>d; // input from user
switch(d) {
case 1: std::cout << a << std::endl;
break;
case 2: std::cout << b << std::endl;
break;
case 3: std::cout << c << std::endl;
break;
default: std::cout << "You have entered wrong no." << std::endl;
}
return 0;
}
Output:
Press 1 to print value of a
Press 2 to print value of b
Press 3 to print value of c
2
100
Here is an example of a Loop Structure
#include <iostream>
using namespace std;
int main()
{
std::cout << "In for loop" << std::endl;
for(int i=1;i<=5;i++)
{
std::cout << "i=" << i <<std::endl ; // for loop will iterates 5 times
}
int j=3;
std::cout << "In while loop" << std::endl;
while(j>0)
{
std::cout << "j=" << j <<std::endl ; // while loop will iterates 3 times
j--;
}
return 0;
}
Output:
In for loop
i=1
i=2
i=3
i=4
i=5
In while loop
j=3
j=2
j=1
Hope this article was helpful to you. Keep Coding Keep Learning.