AS Computer Science Section 2

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Watch the videos linked below to learn why others write computer code and what advantages it can bring to your life.

What most schools don't teach https://www.youtube.com/watch?v=nKIu9yen5nc Luna Ruiz: Why I Code https://www.youtube.com/watch?v=6cKaok1F1P0 David Karp: How to start coding now https://www.youtube.com/watch?v=__NKemV0SzE

One method of representing an algorithm is to use pseudocode. Pseudocode is the process of designing a solution to a problem using a language similar to English.

A trace table is a debugging method that shows the value of variables at each stage of program execution. DECLARE num : INTEGER DECLARE index : INTEGER DECLARE sum : INTEGER Num &#60;&#8212; 3 FOR index &#60;&#8212; 1 TO 4 Sum &#60;&#8212; num ** index IF (sum + index) MOD 10 = 0 THEN OUTPUT (sum + index) END IF NEXT index

The four cornerstones of Computational Thinking are:

A procedure is a section of code in a computer program which can be executed (or &#8220;called&#8221;) from other areas of the program. Each procedure can accept some or no parameters which can be used within the procedure code. It is said that these parameters have been &#8220;passed&#8221; into the procedure.

Algorithms are executed one line at a time, in sequence, from the top to the bottom. It is good practice to include your algorithm within a Python program as &#8220;internal commentary&#8221;. Each comment starts with a #.

Selection is the process of evaluating conditions to then take different paths through the algorithm. There are many ways to represent selection but at this point in the course we will focus on IF... ELSE constructs.

Module libraries are separate files which contain commonly used procedures or functions. These module libraries can be imported into another computer program and used. The advantages of module libraries are:

You can create your own module libraries. These contain what are known as user-defined functions and procedures.

1. The code is pre-written 2. The code is pre-documented 3. The code is pre-tested

The data types are: - String : Holds a sequence of alphanumeric characters e.g. &#8220;Saturday&#8221; - Char : Holds one alphanumeric character e.g. &#8220;z&#8221; - Integer : Holds whole numbers e.g. 42 - Real : Holds numbers which have a decimal point e.g. 42.75 - Boolean : Holds only two values True or False

Algorithms can request information from the user or display it to the user. In Python all inputs are stored as string data types unless explicitly converted. In the example below we have used the INT() function to convert the user input into a whole number.

Iteration is the process of repeating sections of an algorithm. There are different ways of expressing iteration but in this book we will concentrate on fixed iteration, where we know how many times to repeat a section of code.

The following pages describe basic programming concepts in Python 3.x. Videos with a green background exemplify pseudocode for that particular concept. Ensure you complete the programming tasks in the workbook AS Programming 1.

A method of debugging that requires the programmer to evaluate the logical order of each line of a program. For example a variable cannot be used in a calculation until it has been initialised; a loop must have a start and an stopping condition.

Variables are named areas of computer memory which are reserved for use by a computer program. They can hold one value of one data type. For example a variable named weekday which holds string data types could be assigned the value &#8220;Saturday&#8221;.

The contents of variables can be changed or used to change other variables within a calculation. For a calculation to be successful the variables must be a numeric data type e.g. integer numbers.

A function is a section of code in a computer program which can be executed (or &#8220;called&#8221;) from other areas of the program and it will return one value. Each function can accept some or no parameters which can be used within the function code. It is said that these parameters have been &#8220;passed&#8221; into the function. Each function then must &#8220;return&#8221; one value to the code which called it.

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