Christmas Revision

Posted: January 9, 2012 in Uncategorized

I done about 3 hours revision. I looked over all the flashcards a couple of times, focused on the software development process and binary as i find those areas quite hard. I took the test and was surprised i got 100%.

The Processor (CPU)

Posted: November 28, 2011 in Uncategorized

This is the Von Neumann Architecture, it can only read from input devices and write to output devices. But it can read and write from both the main memory and backing storage:

Its made up of Input devices such as keyboard, mouse and scanner. The main memory (RAM). Output devices such as the monitor and printer. The processor (CPU) and the Backing storage.

The Processor is made up of the Control Unit, Registers, ALU, Memory Address Register and Memory Data Register.

The Control Unit manages the fetching, decoding and executing of instructions. The ALU stands for Arithmetic and Logic Unit and carries out calculations such as 00011100 + 11100110 and Logical operations such as AND, NOT and OR. Other General Registers are very fast temporary storage locations which hold:

  • Data being processed
  • Instructions being executed
  • Address of memory locations to be accessed

There are also two other registers which are called the Memory Address Register and the Memory Data Register. Firstly being the MAR ( Memory Address Register) which is where the address of the memory is held. This informs the main memory which memory location will be read or used to store data. Secondly is the MDR ( Memory Data Register) which stores data in a memory location and reads the data from a memory location.

All these parts of the processor are connected up by buses. Buses are physical wires which transmit information and connect each part of the processor together. They also connect the processor to other parts of the computer system such as the Main memory or Backing storage.

 

Bit-mapped Graphics

Posted: November 4, 2011 in Uncategorized

A pixel is a tiny dot on the computer screen. The resolution makes up the quality of the picture. There are two graphics packages that can be used Bit-mapped Graphics(painting) or Vector Graphics (Drawing). A computer represents colours using binary (0 and 1). Each pixel is represented by one bit. The colour black will be 1 and the colour white will be 0. For colours such as Red or Blue, they are represented by 2 bits (00 and 11).

Macros, Scripting, Modularity

Posted: September 26, 2011 in Uncategorized

High level languages are the easiest programming language to learn as it is close to the English language. High level languages use words such as If, Else, Repeat, While, etc. However, the computer cannot understand high level languages as it only understands binary codes which are referred to in programming as machine codes e.g. 100101100110 11001010. These languages are known as Low level languages.

Macros work by recording a series of keypresses which can then be played back as many times as required at a later date for the user. Scripts provide the same benefits, but instructions are given in a script or program. This means there will be no syntax errors.

There are two different types of parameters, Actual parameters and Formal parameters. Actual parameters are passed in to the subroutine when it is called from another part of the program. Formal parameters are used in the subroutine definition.

There are two types of subroutines, procedures and functions. The difference is that a procedure produces an effect and a function produces a value.

Documentation:

Documentation is designed to help the user understand how to use the software program they are using.

There are two pieces of Documentation:

User Guide-The User Guide explains how to use the software. The user guide can be in the form of paper, but more recent it is produced as an electronic file or as online help.

Technical Guide-This gives the user help on how to install the software. Shows what requirements are need for the software(memory and processor requirements). It includes the version number of the software and details of any other files or programs which may need to be installed.
Other types of Documentation may include:

Quick Start Guide– This tells the users the basic information about what they are using. These can be a small booklet, a leaflet or maybe a poster.

Shortcut Guide– This tells the users how to use shortcuts. Shortcuts are a combination of keys that are pressed to perform a certain function in a faster way. For example when we want to copy something we use CTRL + C and to paste we use CTRL + V.

Video Tutorial- This is a video showing the user how to work the program or just showing where all the buttons are.

FAQ’s- This stands for Frequently Asked Questions. These are questions that are repeatedly asked by users that may have the same problem.

Evaluation:

The evaluation stage of the software development process requires the client and developer to review the software. Does the software meet the user requirements? Is it fit for purpose? (Does it do what its supposed to do).

The software also gets evaluated by the following criteria:

Robustness- should not fail no matter what input is entered by the user.

Reliability- is free of design and coding bugs, correct for all specified output. It should work correctly every time it is run.

Portability- It can run on other computers not just the one it was designed on.

Efficiency- should not require processor time or storage resources disproportional to the scale of the program.

Maintainability- subsequent changes can be effected easily and quickly.

The software should be evaluated by client and developer at all stages in the process, not just when the software is complete.

Maintenance:

Making changes to the software after it has been handed over to the client, and enters productive use.

There are 3 types of maintenance activities:

Corrective– Fixing bugs/removing errors

Adaptive-Changes to the environment in which the software operates means necessary changes to the code. Could be updated operating system, or new hardware.

Perfective-Responding to user requests for changes in functionality or addition features

There are factors which can affect maintenance. These are:

New applications, staff mobility, too many versions, insufficient documentation and external hardware and software changes.

The cost of maintenance will vary from one project to another. It is estimated that between 40% and 70% of the costs are spent on maintenance.

 

 

Testing

Posted: September 12, 2011 in Uncategorized

The cost of testing can vary from project to project. Testing begins at the analysis and design stages, with prototypes being developed. It reduces the cost to fix problems at the earlier stages of the software development process as you wouldn’t need to restart the whole program if you found a problem later on. There can be many common errors such as incomplete logic, the programmer hasn’t thought of all the special cases or bad time planning. Normal Data- a normal data set should be tested to show that the program works as expected. Boundary Data(Extreme Data)- A boundary data set is used to test the boundary limits within a program. Exceptional Data(Out of Range Data)- Exceptional data is used to test that the program can properly handle unexpected inputs.

Debugging With RealBasic

Posted: September 8, 2011 in Uncategorized

When you open your RealBasic program and click the button with your code on it, there will be small grey dashes at the side of each line of code. If you click one of the dashes it sets a red dot on that line which represents a break point in your program. If you click the run button and try your program it will redirect you to the code and it will show you the variables to the right. When you click the Step button you can watch your variables change step by step.