# help me to improve this program please

R

#### rami-madini

given two square matrices A & B of size n. based on user selection,
preform one of the following operations:

* Note A={a b} inverse A^-1= (1/ad-be){d -b}
{c d} {-c a}

this is my project for the c++ class I have read all of the instructions that i had received in my last

this is my program help me pleas to improve it and thank you all

#include<iostream>
using namespace std;

void main()
{
float A[10][10], B[10][10], C[10][10],h; int i, j, k, m, n, x, y, Select, c1;

cout<<"Welcome to the matrix calculator \n";
again:
cout<<endl<<endl<<endl;

cout<<"Select One Operation : \n"
"(1)Addition, Subtraction, or Multiplication of A & B\n "
"(2)Transpose of A or B\n"
"(3)Inverse of A or B only when n= 2\n";

cin>>Select;

if(Select==1)
{
cout<<"choose: (1) For Addition.\t(2) For Subtraction.\t(3) For Multiplication.\n";
cin>>c1;

if(c1==1)
{
cout<<"Enter matrix dimensions:\n";
cin>>m>>n;

cout<<"\nEnter Matrix A values:\n";
for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{
cin>>A[j];
}
}

cout<<"\nEnter Matrix B values:\n";
for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{
cin>>B[j];
}
}

cout<<"\nSum of Matrix A and B:";
for(i=0; i<m; i++)
{
cout<<"\n";
for(j=0; j<n; j++)
{
C[j]=A[j]+B[j];
cout<<C[j]<<"\t";
}
}
}

else if(c1==2)
{
cout<<"Enter matrix dimensions:\n";
cin>>m>>n;

cout<<"\nEnter Matrix A values:\n";
for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{
cin>>A[j];
}
}

cout<<"\nEnter Matrix B values:\n";
for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{
cin>>B[j];
}
}

cout<<"\nSubtraction of Matrix A and B:";
for(i=0; i<m; i++)
{
cout<<"\n";
for(j=0; j<n; j++)
{
C[j]=A[j]-B[j];
cout<<C[j]<<"\t";
}
}
}

else if(c1==3)
{
cout<<"Enter Matrix A dimensions:\n";
cin>>m>>n;

cout<<"\nEnter Matrix A values:\n";
for( i = 0 ; i < m ; i++)
{
for( j = 0 ; j < n ; j++)
{
cin>>A[j];
C[j]=0;
}
}

cout<<"Enter Matrix B dimensions:\n";
cin>>x>>y;

cout<<"\nEnter Matrix B values:\n";
for( i = 0 ; i < x ; i++)
{
for( j = 0 ; j < y ; j++)
{
cin>>B[j];
}
}

for( i = 0 ; i < m ; i++)
{
for( j = 0 ; j < y ; j++)
{
for( k = 0 ;k < n ; k++)
{
C[j] += A[k]*B[k][j];

}
}
}

cout<<"\nThe Multiplication of Matrix A and B:";
for( i = 0 ; i < m ; i++)
{
cout<<"\n";
for( j = 0 ; j < y ; j++)
{
cout<<C[j]<<"\t";
}
}
}
}

else if(Select==2)
{
cout<<"Enter Matrix dimensions:\n";
cin>>m>>n;
cout<<"\nEnter Matrix Values:\n";

for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{
cin>>A[j];
B[j]=A[j];
}
}

cout<<"\nThe transpose of the Matrix :";

for(i=0; i<n; i++)
{
cout<<"\n";
for(j=0; j<m; j++)
{
cout<<B[j]<<"\t";
}
}

}

else if(Select==3)

{
cout<<"Enter Matrix dimensions:\n";
cin>>m>>n;
if(n==2)
{
cout<<"\nEnter Matrix Values:\n";

for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{

cin>>A[j];

}
}

cout<<"\nThe Inverse of the Matrix :\n";

h=(1/(((A[0][0])*(A[1][1]))-((A[0][1])*(A[1][0]))));
cout<<(A[1][1]*h)<<"\t"<<(-A[0][1]*h)<<"\n"<<(-A[1][0]*h)<<"\t"<<(A[0][0]*h);
}

else
cout<<"Invaled Input! Please read the statment again carefully this time ";
}
else
cout<<"Invaled Input! Please read the statment again carefully this time ";

goto again;
cout<<endl;
system("pause");

}

and thank you

Ad

B

#### Barry Schwarz

There are several things you can and should do.

One is realize that coding is one of the last steps in developing
a program. Long before you code the first line, you should "design"
your solution to the problem. This will help you put things in proper
order, allow you to recognize blocks of common processing which should
be implemented as separate functions, and identify other processing
which could benefit from being in separate functions (to make the code
easier to read, to simplify debugging, etc).

Another, with a surprisingly high benefit for such a simple
change, is to learn to indent consistently. The body of functions,
the members of structures, the range of if and for statements, should
be indented a visually discernible, but not excessive, amount. Most
have found 3-5 space optimum.

given two square matrices A & B of size n. based on user selection,
preform one of the following operations:

* Note A={a b} inverse A^-1= (1/ad-be){d -b}
{c d} {-c a}

this is my project for the c++ class I have read all of the instructions that i had received in my last

this is my program help me pleas to improve it and thank you all

#include<iostream>
using namespace std;

void main()

In a hosted system, main always returns int. ALWAYS!
{
float A[10][10], B[10][10], C[10][10],h; int i, j, k, m, n, x, y, Select, c1;

While float is obviously acceptable, double is intended to be the
natural floating point type for the system. There is almost no
benefit to float unless you are really short of memory.

Place only one declaration or statement on a line. Furthermore, it
will simplify debugging if you place each object in its own
declaration.

The use of capital letters for simple local variables serves mostly to
complicate typing.
cout<<"Welcome to the matrix calculator \n";

Invest in horizontal white space. It is cost free and makes your code
much more readable.

Labels and goto statements are never required and rarely appropriate.
Try to use a loop for this.
cout<<endl<<endl<<endl;

Excessive horizontal white space makes the code harder to follow and
discourages others from helping.
cout<<"Select One Operation : \n"
"(1)Addition, Subtraction, or Multiplication of A & B\n "

Never include tabs in a string literal. If you want a tab in the
output (which is not the case here), use the \t escape sequence.
"(2)Transpose of A or B\n"
"(3)Inverse of A or B only when n= 2\n";

Look at what your formatting does. First, the code is difficult to
read. Second, the output to the user is not aligned:
Select ...
(1)...
(2)...
(3)...
(4)...

Consider coding it as:
cout << "Select ...\n"
" (1) ...\n"
...
" (4) ...\n";
cin>>Select;

if(Select==1)
{
cout<<"choose: (1) For Addition.\t(2) For Subtraction.\t(3) For Multiplication.\n";

In this type of case, it is common to replace the \n with a few spaces
so the user's input immediately follows the prompt.
cin>>c1;

if(c1==1)
{
cout<<"Enter matrix dimensions:\n";
cin>>m>>n;

cout<<"\nEnter Matrix A values:\n";
for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{

You might consider adding a prompt here
cout << "Enter the value for row "
<< i << " column "
<< j << ": ";
to make life easier for your user.
cin>>A[j];
}
}

cout<<"\nEnter Matrix B values:\n";
for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{
cin>>B[j];
}
}

cout<<"\nSum of Matrix A and B:";
for(i=0; i<m; i++)
{
cout<<"\n";
for(j=0; j<n; j++)
{
C[j]=A[j]+B[j];
cout<<C[j]<<"\t";

Since you don't use C, why not just print the value of the sum? If
you have learned about the iomanip header, you would be better off
using a fixed width and left justification instead of tabs. With
tabs, your data can look like (view with fixed font)
1 2 3
11 22 33
With iomanip, it could look like
1 2 3
11 22 33
else if(c1==2)
{

This entire block of code except for the subtraction is identical to
the c1==1 case.
cout<<"Enter matrix dimensions:\n";
cin>>m>>n;

cout<<"\nEnter Matrix A values:\n";
for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{
cin>>A[j];
}
}

cout<<"\nEnter Matrix B values:\n";
for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{
cin>>B[j];
}
}

cout<<"\nSubtraction of Matrix A and B:";
for(i=0; i<m; i++)
{
cout<<"\n";
for(j=0; j<n; j++)
{
C[j]=A[j]-B[j];
cout<<C[j]<<"\t";
}
}
}

else if(c1==3)
{
cout<<"Enter Matrix A dimensions:\n";
cin>>m>>n;

Before accepting values for A, you should get the dimensions for B and
insure they are compatible with multiplication.
cout<<"\nEnter Matrix A values:\n";
for( i = 0 ; i < m ; i++)
{
for( j = 0 ; j < n ; j++)
{
cin>>A[j];
C[j]=0;
}
}

cout<<"Enter Matrix B dimensions:\n";
cin>>x>>y;

cout<<"\nEnter Matrix B values:\n";
for( i = 0 ; i < x ; i++)
{
for( j = 0 ; j < y ; j++)
{
cin>>B[j];
}
}

for( i = 0 ; i < m ; i++)
{
for( j = 0 ; j < y ; j++)
{
for( k = 0 ;k < n ; k++)
{
C[j] += A[k]*B[k][j];

If you don't check the dimensions, you don't know if A[k] or
B[k][j] even exist.
}
}
}

cout<<"\nThe Multiplication of Matrix A and B:";
for( i = 0 ; i < m ; i++)
{
cout<<"\n";
for( j = 0 ; j < y ; j++)
{
cout<<C[j]<<"\t";
}
}
}
}

else if(Select==2)
{
cout<<"Enter Matrix dimensions:\n";
cin>>m>>n;
cout<<"\nEnter Matrix Values:\n";

for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{
cin>>A[j];
B[j]=A[j];
}
}

cout<<"\nThe transpose of the Matrix :";

for(i=0; i<n; i++)
{
cout<<"\n";
for(j=0; j<m; j++)
{
cout<<B[j]<<"\t";
}
}

}

else if(Select==3)

{
cout<<"Enter Matrix dimensions:\n";
cin>>m>>n;

Why are you asking for dimensions when the value for each has to be 2?

What does your code do if m is not 2?
{
cout<<"\nEnter Matrix Values:\n";

for(i=0; i<m; i++)
{
for(j=0; j<n; j++)
{

cin>>A[j];

}
}

cout<<"\nThe Inverse of the Matrix :\n";

h=(1/(((A[0][0])*(A[1][1]))-((A[0][1])*(A[1][0]))));

You have way to many parentheses.
h = 1 / ( A[0][0]*A[1][1] - A[0][1]*A[1][0] );
cout<<(A[1][1]*h)<<"\t"<<(-A[0][1]*h)<<"\n"<<(-A[1][0]*h)<<"\t"<<(A[0][0]*h);

None of these parentheses serve any purpose.
}

else
cout<<"Invaled Input! Please read the statment again carefully this time ";

An error message should tell the user where he made the mistake. Here
n was not 2.
}
else
cout<<"Invaled Input! Please read the statment again carefully this time ";

Here, Select was not 1, 2, or 3. But 4 is a valid input which you do
not accept.
goto again;

When posting code, convert your tabs to spaces since not everyone has
the same setup you do.

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