Chapter 3: Structured Program Development
=========================================
* Before writing a program to solve a problem, understand the problem
and plan for it first.
* Any computing problem can be solved by executing a series of
actions in a specific order.
* A procedure for solving a problem in term of
1. The actions to be executed
2. The order in which these actions are to be executed
* This procedure is called an algorithm.
* Specifying the order in which statements are to be executed in a
computer program is called program control.
* Pseudocode is an artificial and informal language that helps
programmers develop algorithms.
* Pseudocode particularly useful for developing algorithm that will
be converted in structure programs.
* Pseudocode is similar to everyday English: it is convenient and
user-friendly although it is not an actual computer programming
language.

* Normally, statements in a program are executed one after the other
in the order in which they are written. This is called sequential
execution.
* Various statements enable the programmer to specify that the next
statement to be executed may be other than the next one in a
sequence. This is called transfer of control.
* All programs could be written in terms of only three control
structures (and without goto or jump), namely the "sequence
structure", the "selection structure" and the "repetition structure".

* A flowchart is a graphical representation of an algorithm or of a
portion of an algorithm. Flowcharts are drawn using certain
special-purpose symbols such as rectangles, diamonds, ovals, and
small circles; these symbols are connected by arrows called
flowlines.
* Flowcharts are also useful for developing and representing
algorithms.

* In C, "selection structure" are
1. if (...) {...} : single-selection structure
2. if (...) {...} else {...} : double-selection structure
3. switch (...) {...} : multiple-selection structure
* In C, "repetition structure" are
1. while (...) {...}
2. do {...} while (...)
3. for (...) {...}
* That is all there is in C. Each C program is formed by combining as
many of each type of control structure as is appropriate for the
algorithm the program implements.

The "If" Selection Structure
----------------------------
* It is used to choose among alternative courses of action.
* E.g.
if (grade >= 60)
printf("Passed\n");
* A decision can be made on any expression - if the expression
evaluates to zero, it is treated as false, and if the expression
evaluates to nonzero, it is treated as true.

The "If/Else" Selection Structure
---------------------------------
* The "if" selection structure performs an indicated action only when
the condition is true; otherwise the action is skipped.
* The "if/else" selection structure allows the programmer to specify
that different actions are to be performed when the condition is true
than when the condition is false.
* E.g.
if (grade >= 60)
printf("Passed\n");
else
printf("Failed\n");
* C provides the conditional operator (?:) which takes three
operands.
1. a condition
2. the value for the entire expression if the condition if true
3. the value for the entire expression if the condition if false
* E.g.
printf("%s\n", grade >= 60 ? "Passed" : "Failed");
* The format control string of the "printf" contains the conversion
specification "%s" for printing a character string.

* Nested "if/else" structures test for multiple cases by placing
"if/else" structures inside "if/else" structures.
* E.g.
if (grade >= 90)
printf("A\n");
else
if (grade >= 80)
printf("B\n");
else
if (grade >= 70)
printf("C\n");
else
if (grade >= 60)
printf("D\n");
else
printf("F\n");
* Or perfer to write as
if (grade >= 90)
printf("A\n");
else if (grade >= 80)
printf("B\n");
else if (grade >= 70)
printf("C\n");
else if (grade >= 60)
printf("D\n");
else
printf("F\n");

* To include several statements in the body of an "if" (or body of
other structures), enclose the set of statements in braces ("{" and
"}").
* A set pf statements contained within a pair of braces is called a
compound statement.
* A compound statement can be placed anywhere in a program that a
single statement can be placed.
* E.g.
if (grade >= 60)
printf("Passed.\n");
else
{
printf("Failed.\n");
printf("You must take this course again.\n");
}

* Note: Don't place a semicolon after the condition in an if
structure.

The While Repetition Structure
------------------------------
* A repetition structure allows the programmer to specify that an
action is to be repeated while some condition remains true.
* E.g.
product = 2;

while (product <= 1000)
product = 2 * product;
* When the condition in the "while" structure becomes false, the
repetition is terminated. Program execution continues with the next
statement after the "while".

Assignment Operators
--------------------
* C provides several assignment operators for abbreviating assignment
expressions.
* E.g. The statement
c = c + 3;
can be abbreviated with the addition assignment operator "+=" as
c += 3;
* The "+=" operator adds the value of the expression on the right of
the operator to the value of the variable on the left of the operator
and stores the result in the variable on the left of the operator.
* Any statement of the form:
variable = variable operator expression;
where operator is one of the binary operator "+", "-", "*", "/", or
"%", can be written in the form:
variable operator= expression;

Increment and Decrement Operators
---------------------------------
* C provides the unary increment operator, "++", and the unary
decrement operator, "--".
* E.g.
c++;
++c;
d--;
--d;
* If increment or decrement operators are placed before a variable,
they are referred to as the preincrement or predecrement operators,
respectively.
* If increment or decrement operators are placed after a variable,
they are referred to as the postincrement or postdecrement operators,
respectively.
* Preincrementing (predecrementing) a variable causes the variable to
be incremented (decremented) by 1, then the new value of the
variableis used in the expression in which it appears.
* Postincrementing (Postdecrementing) a variable causes the current
value of the variable to be used in the expression in which it
appears, then the variable to be incremented (decremented) by 1.
* E.g.
#include <stdio.h>

main()
{
int c;

c = 5;
printf("%d\n", c);
printf("%d\n", c++);
printf("%d\n\n", c);

c = 5;
printf("%d\n", c);
printf("%d\n", ++c);
printf("%d\n", c);

return 0;
}
* It is important to note that when incrementing or decrementing a
variable in a statement by itself, the preincrement and postincrement
forms have the same effect.
* Only a simple variable name may be used as the operand of an
increment or decrement operator.

* The data type "float" can be used to handle numbers with decimal
points (called floating-point number).
* C provides the unary cast operator (explicit conversion) to produce
a floating-point calculation with integer values. E.g.
average = (float) total / counter;
* To ensure that the operands of a operator are of the same type, the
compiler performs an operation called promotion (implicit conversion)
on selected operands.


* Execrise
1. A class of ten students took a quiz. The grades (integers in
the range 0 to 100) for this quiz are available to you. Determine
the class average on the quiz.
2. Develop a class averaging program that will process an
arbitrary number of grades each time the program is run.
3. A college offers a course that prepares students for the state
licensing exam for real estate brokers. Naturally, the college
wants to know how well its students did on the exam. You have
been asked to write a program to summarize the results. You have
been given a list of these 10 students. Next to each name is
written a 1 if the student passed the exam and a 2 if the student
failed. Your program should display a summary of the test results
indicating the number of students who passed and the number of
students who failed. If more than 8 students passed the exam,
print the message "Raise tuition".