Unit 2:

ACTIVE &  PASSIVE VOICE

PRESENTATION 1:  Look at the diagram below and study the text!

                    Pulley                string

                                                 
                                                              block

                                          slope

                   weight

The  block rests on a slope.  A string  is attached  to one end  of the  block and passes over a pulley at the top of the  slope.   A weight is suspended  from the end of the string.  When  the block slides down the slope, it pulls the  string and lifts the weight.  At the same time, the pulley rotates  in  a clockwise direction.

WE CAN SAY:   1.  The block PULLS the string. (Active Voice = A)
2.  The string ROTATES the pulley. (A)
                              3.  The string LIFTS the weight. (A)
                                         OR:   4.   The string IS PULLED by the block. (Passive Voice = P)   
5.	The pulley IS ROTATED by the string. (P)
6.	The weight IS LIFTED by the string. (P)

PRESENTATION 2: Study the pairs of ACTIVE and PASSIVE sentences  below!
ACTIVE     :   The engineer   measures      the volume.
PASSIVE    :   The volume     is measured   (by the engineer).

 1. The engineer     is measuring       the volume.   
     The volume       is being measured             (by the engineer).
 2.   ............            has measured                      .................. 
       ............            has been measured              .................. 
 3.   ............            has been measuring             ..................    
       ...........             has been being measured    .................. 
 4.   ............            measured                  ..................       
       ............            was measured           ..................
  5.  ............            was measuring             ..................       
       ............            was being measured        ..................  
 6.   ............            had measured              ..................
       ............            had been measured         ..................  
 7.  ............             will measure              ..................       
      ............             will be measured          ..................  
 8.  ............             is going to measure       ..................       
      ............             is going to be measured   ..................  
 9.  ............             must measure              ..................       
       ............            must be measured          ..................
10.  ............            should measure            ..................       
       ............            should be measured        ..................

EXERCISE:        -  Kenali bentuk AKTIF atau PASIF  pada setiap kalimat!                           
                             -  Tandai SUBJECT dan PREDICATE pada setiap kalimat !

1.  What is a PC? 
A PC is designed to fit on a desk-top.  The IBM PC was introduced in the early eighties and since then has been modified and improved.  Subsequent PCs have been designed to run any software written for previous versions of the PC.  Many other manufacturers have produced compatible computers; that is, computers which work in the same manner as the IBM PC and use the same software. These are often known as clones. 

2. The Components of a PC 
A PC consists of a main unit (or system box), monitor, keyboard and peripherals (see figure 1). Peripherals include devices such as printers and the mouse.  (I)

                                                            Figure 1 Components of a PC 
The main unit contains the Central Processing Unit (CPU) and various supporting Integrated Circuits (or chips).  They are are fixed to a printed circuit board (PCB) called the motherboard. The main unit also houses disk drives, expansion slots and the power supply. (II)
The CPU (Central Processing Unit) or processor, the `brain' of any computer system. is contained on a single Integrated Circuit or `chip'. The CPU processes all instructions and data. (III)
The CPU is driven by an internal clock. Simply speaking, every time the clock pulses the CPU processes one instruction. Thus, the faster the clock the quicker the CPU processes its instructions. Clock speed is measured in MegaHertz (MHz).     (IV)
All PCs are fitted with a certain amount of workspace memory called Random Access Memory (RAM). This memory is used for storing running software and data which the software requires, as well as the operating system. The contents of RAM are lost when the PC is switched off. RAM is located in chips situated on the motherboard. (V)
Disk drives provide a means of storing work, or data. Floppy disks are transportable from PC to PC and come in two sizes, 31/2" and 51/4" diameter. Hard disks are fixed inside the system unit and have much higher storage capacities than floppies. Disk drives are discussed in sections 4 and 5. (VI)
Information is stored on disk in the form of files. Files can be grouped together on disk in directories.  (VII)

3. Ports and Expansion Slots 
Located at the rear of the PC are various sockets or ports. These allow the keyboard and monitor to be connected. Most PCs include a parallel port (usually used for printers) and two serial ports, usually used for communications with other computer systems or connecting mice and plotters. (I)
Also included inside the system box are expansion slots. These allow extra hardware to be added to the PC using printed circuit boards, or cards, plugged into the expansion slots. The slots are connected to the CPU via the bus. The bus is a set of wires which transfers data. (II)

4. Operating System 
An essential part of any computer is its operating system. An operating system provides the links between the computer hardware, the user, and software which is running on the computer system and controls all the components of the computer, including its peripherals. 

5.  The Start Up Procedure
Start up, or boot up as it is often called, is the process of readying the hardware and software for use. The disk with the operating  system files on it is often called a bootable disk since this disk can be used to start up the system.  (I)
Startup is performed each time the computer is switched on. The startup procedure copies the internal operating system commands into the PC's memory, where they will remain until the system is restarted or switched off.  (II)

6. About the I/O buses

   Introduction to the I/O buses
   The PC's buses provide the data "highways" on the system board. The "first" bus is the system 
   bus, which connects the CPU with RAM. In older designs it was a local bus. In newer designs 
   this bus is called the front side bus (FSB). (I)

   The typical local bus has a speed and width depending on the type CPU installed on the    
   motherboard. Typically, the system bus will be 64 bits wide and run at 66, 100 or 133 MHz. 
   These high speeds create electrical noises and other problems. Therefore, the speed must be 
   reduced for data reaching the expansion cards and other more peripheral components.
   Very few expansion cards can operate at more than 40 MHz. Then the electronics shut down. The 
   chips can just not react faster. Therefore, the PC has additional buses. (II)

   What does an I/O bus do?
I/O buses connect the CPU to all other components, except RAM. Data are moved on the buses from one component to another, and data from other components to the CPU and RAM. The I/O buses differ from the system bus in speed. Their speed will always be made lower than the system bus speed. Over the years, different I/O buses have been developed. On modern PCs, usually four buses can be found: 
•	The ISA bus, which is an old low speed bus, soon to be excluded from the PC design. 
•	The PCI bus, which is a new high speed bus. 
•	The USB bus (Universal Serial Bus), which is a new low speed bus. 
•	The AGP bus which solely is used for the graphics card.      (I)
As mentioned earlier, I/O buses provide extensions to the system bus. On the motherboard, the system bus ends in a controller chip, which forms a bridge to the I/O buses.  (II)
All in all, the buses have occupied a very central placement in the PC's data exchange. Actually, all components except the CPU communicate with each other and with RAM via the different I/O buses. Here you see a demonstration of this logic:  (III)

The physical aspects of the I/O buses
Physically, the I/O bus consists of tracks on the printed circuit board. These tracks are used as: 
•	Data tracks, which each can move one bit at a time 
•	Address tracks, which identify where data should be sent to 
•	Other tracks for clock ticks, voltage, verification signals, etc. 

When data are sent on the bus, they must be supplied with a receiver. Therefore, each device on the bus is given  an address. Similarly, the RAM is divided in sections, each having its address. Prior to sending data, a number is sent on the address track, to identify where the data should be sent to. 

The bus width
The number of data tracks determine the data transfer capacity. The ISA bus is slow, partly because it only has 16 data tracks. The modern PCs send 32 bits per clock tick. On the ISA bus, 32 bits must be divided in two packages of 16 bits. This delays the data transfer. Another I/O bus concept is wait states. 

Wait states 
Wait states are small pauses. If an ISA adapter cannot keep up with the incoming data flow, its controller sends wait states to the CPU. Those are signals to the CPU to "hold on for a sec." A wait state is a wasted clock tick. The CPU skips a clock tick, when not occupied. Thus the old and slow ISA adapter can significantly reduce the operating speed of a modern computer.