Lecture 2 Programming life cycle

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

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.

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.

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

Sample pseudocode 2 Registration 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.

Sample pseudocode 1 average 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 = nstudents+1 – read another grade from user – add grade to sum avg=sum/nstudents print avg to the screen