Programming Principles & Practices Using C++ - Ch 04 'Try This' exercise - c++

Question

I'm a bit confused about this exercise in the above mentioned book-
"The character 'b' is char('a'+ 1), 'c' is char('a'+ 2), etc. Use a loop to write out a table of characters with their corresponding integer values:
a 97
b 98
c 99
...
z 122"
The book has just gone over while loops, and I read a bit ahead as I was still confused as to how to do this without just listing out each value individually (which I assume isn't the point here), and the next section is about for loops. I thought that maybe you can somehow increase letters in the alphabet by 1 in a loop (so a -> b, b -> c, etc.), but if this is indeed possible, the book hasn't yet gone over how to accomplish this yet.
Thanks in advance, I'm working through this book alone in my spare time so I don't have a professor to ask questions like this, and the Try This exercises don't have their answers listed on Bjarne's website.

Answer 1

Just write a simple loop:
for(auto c = 'a';c <= 'z' ;c++)
cout<<c<<" "<<int(c)<<endl;

Answer 2

Here is my solution to your problem :)
int main (void) {
char c = 'a';
while (c <= 'z') {
std::cout << c << "\t" << c - 0 << '\n'; // c - 0 is convertion to int without cast
++c;
}
return 0;
}

Answer 3

The book is referring to the idea that you can iterate over integers and use the control variable in character arithmetic to get the table. For example, with integers you can iterate over the integers 0 to 25 with
int i = 0;
while (i <= 25) {
cout << i << endl;
i = i + 1; // or ++i
}
Now you can apply the problem hint char('a' + i) to get the rest of the answer. I'll let you work that out.

Answer 4

int main()
{
char ch = 'a';
int i = 0;
while(i < 26)
{
cout << (char)(ch + i) << "\t" << (ch + i) << "\n";
++i;
}
}

Answer 5

You can do something like this:
char ch = 'a';
for (int i = 0; i < 26; ++i)
cout << (char)(ch + i) << " " << (ch + i) << endl;
This will generate the output that you expect.

Answer 6

Here is one way to do it using the while loop:
#include <iostream>
int main()
{
int i = 0; //Initialize i to 0.
while (i < 26) // 0 - 25.
{
int val = 'a' + i; // char('a' + 1), int('a' + 1).
std::cout << char(val) << "\t" << int(val) << std::endl;
++i; //Increments the while loop variable i
}
return 0;
}
Output:
a 97
b 98
c 99
d 100
e 101
f 102
g 103
h 104
i 105
j 106
k 107
l 108
m 109
n 110
o 111
p 112
q 113
r 114
s 115
t 116
u 117
v 118
w 119
x 120
y 121
z 122

Answer 7

I included comments so that you can understand my thoughts and also so that it can be updated.
Here's the answer to the Chapter 4 Try this exercise for the book by Bjarne Stroustrup: Programming Principles and Practice Using C++:
// Description- Try this exercise using a while statement to provide a series of characters from the ASCII code.
#include "stdafx.h"
#include "Std_lib_facilities.h"
int main()
{
int i = 96; // Beginning/initialisation of the integers which will be converted to char (s) in cout.
while (i<122) // The limit for the while statement is the integer which will be safely converted to the last char.
{
cout << i + 1 << '\t'<< char (i+1)<<'\n'; ++i; // The first integer will be 1 plus the initial = 97. Then followed by a tab.
// Then followed by the integer 97 being safely converted to an char using the ASCII.
// The while loop in the two comments is repeated till 122 is converted safely to z.
}
}