Types define how we will use particular set of bits.
Functions allow us to specify operation that will be performed on data.
C++ Structures to group heterogenous data together.
Pointers to refer to information indirectly.
Basic Data types are
We can trade space for accuracy and use int , long int, short int for integers and from float, double for floating-point numbers.
Ops are associated with types not other way around. Keep track of whether operand and result are of correct type. In some situation C++ performs implicit type conversion in other cases we perform casts.
Functions have a list of arguments and possibly a return type. First line includes the library which contains cout and endl.
#include <iostream.h>
int lg(int);
int main(){
for( int N =1000;N<=1000000;N*=10)
cout<<lg(N) <<" "<<N<<endl;
}
int lg(int N){
for(int i=0;N>0;i++,N/=2);
return i;
}
By not specifying the type of the numbers that the program processes, we extend its potential utility, portability.
Best Practice is to split file in 3 files.
Reusing function names or operators in different data types is called overloading.
Simplest mechanism to group data in C++ is arrays and structures.
Structures are aggregate types that we use to define collections of data such that we can manipulate an entire collection as a unit, but still can refer back to components of a given datum by name.
struct point {float x; float y;};
float distance(point,point);
so we can now declare the variables using this new data type.
struct point a,b; declared two variables of this type.
also note that we can pass this data type as arguments to the functions.
a.x = 1.0; a.y = 1.0 This can be considered as initialization of variables.
#include <math.h>
#include "Point.h" //interface file
float distance(point a,point b)
{
float dx = a.x - b.x , dy = a.y-b.y;
return sqrt(dx*dx+dy*dy);
}
Now pointer gives us ability to manipulate our data indirectly. A pointer is a reference to an object in memory.
int *a Here variable a is a pointer to integer.(Declaration)
*a refers to that integer. (Accessing)
Unary Operator & gives machine address of an object and useful in initializing pointers. For e. g. *&a is same as a.
polar(float x, float y, float *r, float *theta)
{ *r = sqrt(x*x + y*y); *theta = atan2(y, x); }
This snippet actually creates a function that return multiple values using pointers with calling function as-
polar(1.0, 1.0, &a, &b) //note arguments are passed by value.
Same effect can be achieved by reference parameters
polar(float x, float y, float& r, float& theta)
{ r = sqrt(x*x + y*y); theta = atan2(y, x); }
float& means “reference to a float”.polar(1.0, 1.0, a ,b) will set a = 1.4142… and b =0.7853….