Now what I want to show is a few algorithms on how to show my imagination on working with indices in matrices.
This first algorithm looks like this :
input : n=4
output :
2 3 5 7
37 41 43 11
31 53 47 13
29 23 19 17

It is a coil out of numbers :p.

#include<iostream.h>

#include<stdio.h>

#include<iomanip.h>
void header();


int n,d,ok,b[100],i,k,j,x,a[20][20];

void main()

{ header();
cout<<"n=";cin>>n;

b[1]=2;

k=2;

x=3;

while(k<=n*n) { ok=1;

for(d=2;d<=x/2;d++) if(x%d==0) ok=0;

if(ok) b[k++]=x;

x++;

}

x=1;

for(k=1;k<=n/2+1;k++) { for(j=k;j<=n-k+1;j++) a[k][j]=b[x++];

for(i=k+1;i<=n-k+1;i++) a[i][n-k+1]=b[x++];

for(j=n-k;j>=k;j--) a[n-k+1][j]=b[x++];

for(i=n-k;i>k;i--) a[i][k]=b[x++];

}

for(i=1;i<=n;i++)

{ for(j=1;j<=n;j++) cout<<setw(2)<<a[i][j]<<" ";

cout<<endl;

}



}
void header()
{ printf("---------------------------------------------------------------\n");
printf("Autor : fl0 fl0w \n");
printf("flo[underscore]flow[underscore]supremacy[at]yahoo[dot]com\n");
printf("---------------------------------------------------------------\n");
}


NExt ..
n=4
m=3
a[1][1]=1
a[1][2]=2
a[1][3]=3
a[2][1]=4
a[2][2]=5
a[2][3]=6
a[3][1]=7
a[3][2]=8
a[3][3]=9
a[4][1]=10
a[4][2]=11
a[4][3]=12
Matricea este
1 2 3
4 5 6
7 8 9
10 11 12
Conturul matricei este
1 2 3 6 9 12 11 10 7 4

Yep you guest good it's the outline of the matrix.

#include<iostream.h>



#include<stdio.h>

int n,m,i,j,a[10][10];

// function prototype

void header();

void main()

{ header();

cout<<"n=";cin>>n;

cout<<"m=";cin>>m;

for(i=1;i<=n;i++)

for(j=1;j<=m;j++)

{ cout<<"a["<<i<<"]["<<j<<"]=";

cin>>a[i][j];

}

cout<<"Matricea este "<<endl;

for(i=1;i<=n;i++)

{ for(j=1;j<=m;j++) cout<<a[i][j]<<" ";

cout<<endl;

}

cout<<"Conturul matricei este "<<endl;

for(j=1;j<=m;j++) cout<<a[1][j]<<" ";
for(i=2;i<=n;i++) cout<<a[i][m]<<" ";

for(j=m-1;j>=1;j--) cout<<a[n][j]<<" ";

for(i=n-1;i>=2;i--) cout<<a[i][1]<<" ";

cout<<endl;



}



void header()

{ printf("---------------------------------------------------------------\n");

printf("Autor : fl0 fl0w \n");

printf("flo[underscore]flow[underscore]supremacy[at]yahoo[dot]com\n");

printf("---------------------------------------------------------------\n");

}

NeXt .. . this program solves any ecuation of degree 2 :
a=5
b=-2
c=-3
Ecuatia are radacini reale si distincte
x1=1
x2=-0.6

#include<iostream.h>
#include<stdio.h>

#
#include<math.h>
#
void header();
int a,b,c,d;
#
float x,x1,x2;
#
void main()
#
{ header();
cout<<"a=";cin>>a;
#
cout<<"b=";cin>>b;
#
cout<<"c=";cin>>c;
#
if(a==0) if(b==0) if(c==0) cout<<"Ecuatie nedeterminata"<<endl;
#
else cout<<"Ecuatie imposibila "<<endl;
#
else { x=(float)-c/b;
#
cout<<"Ecuatie de gradul intai ,x="<<x<<endl;
#
}
#
else { d=b*b-4*a*c;
#
if(d<0) cout<<"Ecuatia are radacini complexe "<<endl;
#
else if(d==0) { x=(float)-b/(2*a);
#
cout<<"Ecuatia are radacini reale si egale,x1=x2="<<x<<endl;
#
}
#
else { x1=(float)(-b+sqrt(d))/(2*a);
#
x2=(float)(-b-sqrt(d))/(2*a);
#
cout<<"Ecuatia are radacini reale si distincte"<<endl;
#
cout<<"x1="<<x1<<endl;
#
cout<<"x2="<<x2<<endl;
#
}
#
}
#

#
}
void header()

{ printf("---------------------------------------------------------------\n");

printf("Autor : fl0 fl0w \n");

printf("flo[underscore]flow[underscore]supremacy[at]yahoo[dot]com\n");

printf("---------------------------------------------------------------\n");

}