Introduction to Programming and Problem Solving (CS101) Lecture 3 PDF

Introduction to Programming and Problem Solving (CS101) Lecture 3 Prepared by/ Ibrahim Shawky  Software engineering (Revist)  Software engineers typically break the software development process (software development life cycle) into the following four...

Introduction to Programming and Problem Solving (CS101) Lecture 3 Prepared by/ Ibrahim Shawky  Software engineering (Revist)  Software engineers typically break the software development process (software development life cycle) into the following four phases:  Analysis  Design  Implementation  Testing and debugging  Software Design  After analyze the problem next step is to design an algorithm to solve the problem.  If you broke the problem into sub problems you need to design an algorithm for each sub problems.  Algorithm: A step-by-step problem-solving process in which a solution is arrived at in a finite amount of time.  There are two Kinds of Design  Structure design  Object oriented design  Structured Design  Also Called: top-down design, stepwise refinement, and modular programming.  Dividing a problem into smaller sub problems.  Each sub problem:  Analyzed, and  A solution is obtained to solve the sub problem.  The solutions of all the sub problems are then combined to solve the overall problem.  This process of implementing a structured design is called structured programming.  Object-Oriented Design  the first step in the problem- solving process is to identify the components called objects and determine how these objects interact with one another.  After identifying the object, the next step is to specify the following attributes for each object:  the relevant data and  possible operations to be performed on that data  Final program is a collection of interacting objects.  This process of implementing an object-oriented design is called object-oriented programing (OOP) language.  Example of Object-Oriented Design  Example: video store  The two main objects are the video and the customer.  For a video object:  The data might include the movie name, starring actors, producer, and so on.  The operations on a video object might include checking the name of the movie, reducing the number of copies in stock by one after a copy is rented.  Software Implementation  In this phase, you write programming code to implement the operation that identified in the design phase.  This course focus on software implementation phase.  Testing and debugging  Testing refers to test the correctness of the program or making sure that the program does what it is supposed to do.  Debugging refers to finding and fixing the errors, if they exist.  To increase reliability of program you must discovery error and fixed it.  Main test types  There are two types of testing:  black-box testing and White-box testing.  black-box testing  The internal working of the function not know  It is only required to know what the function does and test it.  So, Black-box testing is based on inputs and outputs.  Example: -  if we make function to check integer if it is greater than or equal to 0 and less than 100  The function is tested on values that surround and fall on the boundaries called boundary value.  Example -1, 1,100  White-box testing.  relies on the internal structure and implementation of a function will be known.  The objective is to ensure that every part of the algorithm is executed at least once.  Example: If statement test when true and false  you need at least one input for if to ensure it work.  Algorithm  A programmer starts with a general idea of a task for the computer to perform.  the programmer has some idea of how to perform the task by hand, at least in general outline.  An algorithm is an unambiguous, step-by-step procedure that terminates after a finite number of steps.  An algorithm is not the same as a program.  An algorithm can be expressed in any language, including English.  Algorithm  The most widely used notations for developing algorithms:  A flowchart is a diagram containing lines representing all the possible paths through the program.  Pseudo-code is a form of stylized (or structured) natural language.  Pseudo-code and stepwise refinement  Pseudo code is a high-level description of a program's logic written in plain language.  It helps to plan out an algorithm before translating it into actual code.  Pseudocode is the intermediate state between an idea and its implementation(code) in a high-level language.  To write algorithm in pseudo-code, you can use the stepwise refinement method.  it’s the type of top-down design (structure design).  Pseudo-code and stepwise refinement  To write your idea in the form pseudo-code, two steps must be performed:  Stepwise  break a complex problem down into a number of simpler steps.  Sub-algorithm can themselves be broken into smaller portions.  Refinement  Refinement continues in this manner until each step is sufficiently detailed  replacing existing steps/instructions with a new version that fills in more details. Example Example Example Example Example Output devices