C++ Programming Guide and Tips

This style guide is mandatory for all submitted work for grading (homework, projects, labs, exams). The purpose of the guide is not to restrict your programming but rather to establish a consistent style format for your programs.

This will help you debug and maintain your programs.
It will help others (including your instructor) to understand them.

Whitespace and Visual Layout

"Whitespace" refers to newlines, space characters and tabs. In source code we do not generally use tabs. In fact, emacs replaces tab characters with an appropriate number of space characters.

In many circumstances whitespace is not required in order for compilers to correctly compile source code, even though the result is unreadable to us. There are three major ways we use whitespace to format code for maximum clarity:

Bad Formatting

#include <iostream>
using namespace std;
int main()
{
// Read first number
double x;
cout<<"Enter first number : ";
cin>>x;
// Read second number
double y;
cout<<"Enter second number: ";
cin>>y;
// Calculate sum
double sum;
sum=x+y;
// Print sum
cout<<"The sum is: "<<sum<<endl;
return 0;
}

Good Formatting

#include <iostream>
using namespace std;

int main()
{
  // Read first number
  double x;
  cout << "Enter first number : ";
  cin >> x;

  // Read second number
  double y;
  cout << "Enter second number: ";
  cin >> y;

  // Calculate sum
  double sum;
  sum = x + y;

  // Print sum
  cout << "The sum is: " << sum << endl;

  return 0;
}

Indentation: Each level of block nesting must be indented by a consistent number of spaces (usually two spaces).
Blank Lines: In source code, use blank lines to separate chunks of code that accomplish distinct tasks. While to some extent this is taste and art, you should expect distinct functions to be separated by blank lines, and a long function body should usually be broken into chunks by blank lines as well.
Whitespace separating elements of code: We recommend using whitespace between operators and operands, except where precedence is highlighted by leaving out spaces.

Good y = 2*y + x/y + 5;

Bad y=2*y+x/y+5;

Comments

Comments should be indented consistently with the block of code they describe. Comments can be divided into two general categories, strategic and tactical.

Filename and Author should be given in the beginning of your code.
Strategic comments are used to give the reader a general overview of what is going on. These comments appear at the beginning of files, before important functions, and above important blocks of code. Strategic comments tend to be written in sentences with an emphasis on explaining the big picture of what the block of code is designed to do.
Tactical comments are designed to explain tricky areas of code, what parameters do, and hints about the control flow of the program. These comments should be intermixed in the code when needed. They should be shorter than strategic comments, in bullet format, and may be in inline format. One should, for instance, place a tactical comment next to the statement that assigns a fixed, non-obvious value to a variable.

The following example shows good commenting. Note the tactical comment about why "9.0" is used instead of "9".

/***************************************************
Filename: f2c.cpp
Author: MIDN Nobody Smith (259999)
Fahrenheit to Celsius Conversion
***************************************************/
#include <iostream>
using namespace std;

int main()
{
  // Read temperature in Fahrenheit
  double Tf;
  cout << "Enter temperature in Fahrenheit: ";
  cin >> Tf;

  // Compute temperature in Celsius
  double Tc;
  Tc = (Tf - 32)*(5/9.0); // .0 forces division as double

  // Write temperature in Celsius
  cout << "That is " << Tc << " degrees Celsius." 
       << endl;

  return 0;
}

Naming

Variables should have meaningful names.
For example, consider a program that uses a variable to track the yards per carry of a football game. Such a variable should be called yardsPerCarry rather than just x for program readability. This must be balanced against using names which are too long. (Fifteen or so characters approaches the "too long" limit.)

Curly Braces, i.e. { }'s

Curly Braces, i.e. { }'s in C++ are used to create a "block" from one or more statements. The delineate the bodies of functions, loops and switch statements, struct definitions, and the then and else blocks of if statments.

Generally, one should either always put the opening curly brace on a new line (preferred for this course) or always but it last on the previous line. Once again consistency is key.
If the opening brace goes on a new line, the preference for this course is to keep the previous line's indentation — i.e. do not indent the curly brace. Generally, curly braces of either kind will occupy their own line, except for rare occasions when an entire block is put on one line. The exception is that comments may follow either opening or closing braces.
The chunk of code inside the newly created block should be indented.

Good Good Bad Bad


while (x < 3)
{
  cout << x << ",";
  x++;
}
cout << endl;


while (x < 3) {
  cout << x << ",";
  x++;
}
cout << endl;


while (x < 3)
{ 
cout << x << ",";
x++; 
} 
cout << endl;


while (x < 3)
{ cout << x << ",";
  x++;
} cout << endl;

Other Tips on Naming

Single letter variables or constants should not be used.
An exception to this rule is when it is common practice to identify something with a single letter. An example of this is the coordinate system (x, y, and z). A second exception occurs in the use of loop counter variables where it is common practice to use variables like i and j as counters in for loops.
Function names and variable names should begin with a lower case letter.
An identifier consisting of multiple names SHALL have each name distinguished by making the first letter of each name part (after the first) upper case (e.g. yardsPerCarry) or by using underscores (yards_per_carry). The former method is strongly encouraged.
Constants should be named in all upper case letters.
Example:
```
const int PI = 3.14;
```
It's generally good to avoid lower case letter 'L', or the letter 'O' in names unless they are part of normal words. This is to avoid confusion with the numbers 1 and 0. For example, is "cell" c- e - 1- ONE or c- e- 1-1?
Avoid names that differ only in case, look similar, or differ only slightly.
For example, InputData, InData and DataInput will certainly be confusing if used in the same program.
Names of functions should reflect what they do (printArray), or what they return (getAge).
Boolean variable names should sound like Yes/No things — "isEmpty" and "isFinished" are possible examples.

Miscellaneous but Important Stuff

No line of code should wrap beyond the right margin. If a line of code becomes too long, break it up into pieces. Remember the compiler largely ignores extra whitespace in your programs (but be careful with strings).
Always use the most appropriate operator or construct for the work you want it to do. Good design and clarity take precedence over optimization. Do not declare or use more variables than are necessary.
Numerical constants ("magic numbers") must not be coded directly. The only allowable exceptions are for 0, 1 or -1, and those which are not likely to change; for example code determining if a number is even can use the number 2 since it is not likely to change. Numerical constants must have a comment explaining the value if it is not evident from the name.

Practical tips for tackling programming problems

Here are a few practical tips that will improve your programming skills.

The more independent a programmer is, the better. Of course, you need to look at lecture notes, sample programs, and other materials to write your program. However, do this before writing the code, but try to avoid looking at them if possible while writing your code. In particular, if you are really new to programming, try to write your code from scratch without doing any copy-and-paste, at least for the first three weeks. I know it's impossible to do so; try with your discretion.
There are some benefits to this approach:
- You will become more conscious which concepts (or less important details) you miss. This way, you can identify your misunderstandings and fix them with more ease.
- You will write a code faster. Access to something in your brain is much faster than in any other storage. Memory hierarchy matters.
- Your brain seems to do creative synthesis. You may gain more fundamental perspectives on programming if you put more in your brain. However, things outside your brain always stay the same to you.
The devil is in the details. Don't forget that is it you as a programmer who are responsible for all the bits and pieces of your program. Things may seem simple at a first look, but usually they will take more time and effort to complete than expected.
As one more example, the online notes sometimes explain technical details. In this case, reading one paragraph may take even 5 minutes or more to work out all the details in your brain. Don't skip through the details. The devil is in the details.
Step back, and think again. When you finish a task, take a brief moment and step back. Check if you get both the big picture logic and the small details to implement the logic. See if there are some inconsistencies and fix them if any.
How valuable is a car that doesn't run? It's useless, and I won't buy the car. Likewise, however many lines your source code may have, if it doesn't work, it's useless, and I won't buy your program. Try to make a good, working product. If your code doesn't work, you are missing something; what is it?

Good	`y = 2*y + x/y + 5;`
Bad	`y=2*y+x/y+5;`