Development of Computers

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Development of Computers The earliest known device to record computations was the abacus. It dates back to ancient times and was invented by the Chinese. Ten beads were strung onto wires attached to a frame. Addition and subtraction were read from the final positions of the beads. It was considered the first manual tool used in calculating answers to problems that provided information and in a primitive way storing the results. Abacus Mechanical Clock During the Middle Ages the first closed system in terms of calculating information was invented by use of a mechanical clock. The parts of the clock calculated the time of day. The time was displayed through the position of two hands on its face. The inventor pre-programmed the clock instructions through the manner in which the pull of the weights and the swing of the pendulum with the movement of the gears established the position of the hands on the clock face. Mathematics John Napier (Scotsman mid 1600s) discovered logarith

Pointing devices

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2. Pointing Devices


these are devices used to control the pointer/cursor on the screen. Examples: mouse, joystick, trackball, light pen etc

   The Mouse

there are different types of mice namely: ps/2, optical, wireless/cordless etc 



Mouse skills

as the mouse moves on a flat surface, it moves a ball beneath or a photosensitive signal that corresponds by moving the pointer/cursor on the screen. 
KCSE Computer Notes
Mouse Parts

 Mouse terminologies


-Clicking- this is pressing the left button of the mouse once to execute a command

-Double clicking- clicking the left button of the mouse twice in quick succession. Used to start an icon

-Drag and drop-this involves clicking on an icon, dragging it, and releasing the button. Used to move and re size objects

-Pointing-moving the mouse pointer to the designated target

Scrolling wheel- used to move hidden text up and down the screen of an active window.

  • Track ball- this is just like a mouse whose ball is located at the top. The pointer on the screen is moved as the user moves the ball with a finger.
 
KCSE computer studies notes
Track Ball

  • Joy stick- looks like a car gear. When the lever like part is moved, the pointer moves on the screen. Mostly used to play games. 
 
kcse computer studies notes
Joy Stick
  •  Light pen and stylus- A light pen, also called a selector pen, is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT display. It allows the user to point to displayed objects or draw on the screen in a similar way to a touch screen but with greater positional accuracy
    kcse comuter tutorials
    Light Pen
     

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