Basic Computer Output & Arithmetic Operations

We will be discussing the basic computer output and arithmetic operations. This tutorial will give you a clue on how computer manipulate its data arithmetically (Arithmetic Operation) and display (Output/Display Operation) the desired result if need be, or it will be stored back inside the computer memory.

Basic Computer Output Operation:

An output operation causes the computer to send a copy of a specified value to a specified output device: An output device includes but not limited to: The Visual Display Unit (VDU) printer, Secondary memory device like the flash drive, hard disk etc. The VDU is the default output device when no particular output device is mentioned.

The value to be sent or displayed may be specified in a variable, as part of instruction specifying the output operation or it can be represented by a (symbolic) constant. All these operation can occur in the same output instruction, if necessary. It means that comma ',' will be used to separate the individual output elements in the instruction just like in the input operation.

During an output operation no value is erased. In other words no destruction of memory content is made as a result of an output operation.

The frequently used verbs to indicate an output instruction or operation include display, show, write, output, print, etc. To specify an output operation am sure you that you write steps such as the following:

• write Name
  print Name, Age
  display Name, Age, Height
  show “Albert Einstein”, Age, Height
  display “The basic personal information of this Physicist is”, Name, Age, height

Notice that the last operation was separated using comma and instead of putting the actual values it was the variables that holds the value that was used instead; the meaning of the action carried out is as illustrated in the figure below:


As you can see, the memory locations remain same at the end of the output operation. This shows that an output operation is not a destructive operation. The three (3) periods, “. . .”, shows that there is omitted information/data contained in the memory. What is contained in the memory locations that was omitted are as displayed in the VDU, in the above diagram.

An output operation is like telling the computer to display on the screen the contents of specified the memory locations as specified in the diagram above. Printers, Digital Signposts, Televisions, and all other devices that are capable to display at least an empty space (white space) or a character are based on this principle.

Basic Computer Arithmetic Operation:

Arithmetic is the branch of pure mathematics dealing with the theory of numerical calculations. An arithmetic operation is an action which is performed on two numbers, known as the operands, to obtain a number, known as the result of the operation. The ordinary arithmetic operations are add, subtract, divide and multiply. If you have being in mathematics class before you will agree with me that the arithmetic operations are denoted with the following operators +, -, ÷ and x, respectively.

In the computer context there are represented as; +, -, /, and *, respectively. An arithmetic operation is same with the algebraic equation and expression.

In everyday algebra, the handling of variables and values can almost be arranged in any order, and you will be forgiven. The following expressions are allowed:

x = 2 or 2 = x,
x = 2 + 3 or 2 + 3 = x
x < 2 or 2 > x...

In the computer context of algebra, you will not be forgiven by the computer t arrange your variable and values/constants anyhow. Study the following expressions:

x = 2     correct
2 = x,    wrong
x = 2 + 3     correct
2 + 3 = x     wrong
x < 2     correct
2 > x …wrong

This means that a variable name must be at the left hand side and the value/constant must be at the right hand side of the equation or expression.

An Arithmetic Logic Unit (ALU) is a unit within the computer Central Processing Unit (CPU) where mathematics is done. One can say that it is a computing or an arithmetic room (office) within the CPU. It is in the ALU Mathematical operation is done.

An arithmetic operation causes the computer to:
i. Send a copy of each operand to the ALU
ii. Signal the ALU to perform the indicated operation and keep the result in a CPU register.

To specify an arithmetic operation be performed one can write:

1. add Age and Height
2. divide height by 2
3. subtract current day from birth day
4. subtract death day from birth day

The mean of the first instruction is as shown below:

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