Programming life cycle

1
Lecture 2

• Programming life cycle

2
computer piano analogy

• Piano player - computer hardware
• Musical score/notes - software or program
• Composer - programmer
• A music box is set with one melody similar to a
  microwave's preset computer chip

3
Algorithm

• An algorithm is a set of steps to accomplish a
  task
• High level language and source code are synonyms.
  Examples include C, C, Pascal, Java, COBOL,
  Fortran, Python
• All these languages have very specific syntax.
  This allows a compiler program to read them and
  translate them into machine code.
• Machine code-the final executable file that can
  be run as an application.

4
HLL, pseudocode, syntax

• All High level Languages (HLL) have similar
  constructs such as a "while" loop, "if then"
  statements and others. Therefore a programmer
  often first writes code in Pseudocode.
• Pseudocode- code that almost source code but
  cannot be run through a compiler since it does
  not have the correct syntax.
• Syntax- the exact proper way a HLL must be
  written in for a compiler program to work.

5
Compiler

• source code machine code
• Source code is stored in a simple text file
• machine code is stored in an executable file or
  an application file.

Compiler
6
Sample pseudocode 2Registration system in BC.

• First we will keep all information in two tables
  (on the hard disk but copied to RAM when the
  program runs
• The first is a students table that has students?
  addresses, courses taken or registered for and
  grades. ?
• The second is a course database that has the
  course number, hours, number enrolled and
  enrollment limit.
• Enter all courses that will be offered this
  semester
• If a new student comes to register enter name
  into student database
• For each course a student wants to take
• i.      If the course is not full, in the course
  table increment the number enrolled and in the
  student table enter the course number for that
  student.
• ii.      If the course is full inform the student
  that they would need an overtally.

7
Sample pseudocode 1average entered grades

• prepare the following three variables (a spot in
  memory to store things)
• nstudents- number of grades entered so far,
  sum-sum of grades so far, avg-average of grades
• while entered grade from user is still not
  negative
• nstudents nstudents1
• read another grade from user
• add grade to sum
• avgsum/nstudents
• print avg to the screen