Another question about syntax

This is a discussion on Another question about syntax within the C++ Programming forums, part of the General Programming Boards category; Group, Again, self teaching has its limitations. Below is code that ultimately will answer question 3: design a program that ...

  1. #1
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    Another question about syntax

    Group,
    Again, self teaching has its limitations.
    Below is code that ultimately will answer question 3: design a program that finds all numbers from 1 to 1000 whose prime factors, when added together, sum up to a prime number.
    I am starting with a string limit of 1 to 100 to keep it manageable.
    I have labeled each unique output with a new name so ultimately I can harvest them. I think a few more iterations will gt me all that I need.
    The problem is,in the code below, the output starts at twenty. I do not understand why it does not output starting at least at 4 / 2 = 2.
    Can anyone help me?
    Thank in advance,
    Dan

    Code:
    #include <iostream>
    #include <string>
    
    using namespace std;
    
    
    
    int i;
    int j;
    int k;
    int l;
    int m;
    
    int main ()
    {
    
    
        // determine what the numbers prime factors are
    for ( int i = 2; i < 100; i++)
    {
    
        for ( int j = 2; j < i; j++ )
        {
            if ( i % j == 0 )
            {
            int k = i / j;
    
                cout << i << " i" << " div " << j << " j" << " = " << k << " k" << "\n";
    
                if ( k % j == 0)
                {
                    int l = j;
                    int m = k / l;
                    cout << "\t" << " and " << k << " k" << " div " << l << " lj" << " = " << m << " m" << "\n";
    
                }
    
            }
    
        }
    }
    
    }

  2. #2
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    The number of lines you output are likely exceeding the size of the console window buffer - which means the first bunch of lines are lost.

    When you have long outputs like this, consider writing the data to a file instead of (or in addition to) stdout, so you can examine everything that was printed.

  3. #3
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    Matticus,
    Thanks for the help. You are saying that I am getting the results that I want and thereby can use them in the next step, it is just that they are not being printed. If I reduce my scope to 50 I would see them.
    Writing the data (output) to a file is later in my learning path. Is it simple to describe?
    Thanks again,
    Dan

  4. #4
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    You are saying that I am getting the results that I want and thereby can use them in the next step, it is just that they are not being printed.
    Well, they are getting printed, but the console window only has a certain amount of space before previous information is "scrolled off" the top.

    If I reduce my scope to 50 I would see them.
    Likely - have you tried?

    Writing the data (output) to a file is later in my learning path. Is it simple to describe?
    My knowledge lies with C, not C++, but there are plenty of tutorials online that explains file I/O. One of them is here.

    C++ File I/O Tutorial - Cprogramming.com

  5. #5
    C++まいる!Cをこわせ! Elysia's Avatar
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    Just don't read from a file into a char array (use std::string). You might get a buffer overflow. I should notify webmaster of that old unsafe code o_O
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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