Which of the following ports on a computer are used to connect a keyboard?
Each correct answer represents a complete solution. Choose two.

A.
USB

B.
DB-25

C.
PS/2

D.
DB-9

Explanation:
The PS/2 and USB ports on a computer are used to connect a keyboard.
What is USB?
Universal Serial Bus (USB) is a high speed bus standard developed by Compaq, IBM, DEC, Intel,
Microsoft, NEC, and Northern Telecom. It provides the Plug and Play capability of Windows to
external hardware devices. USB supports hot plugging, which means that a USB device can be
installed or removed while the computer is running. A single USB port can be used to connect up to
127 peripheral devices, such as CD-ROM drives, tape drives, keyboards, scanners etc. USB 1.1 has a
maximum data transfer rate of 12 Mbps, whereas USB 2.0 has a maximum data transfer rate of 480
Mbps. USB 2.0 is fully backward compatible with USB 1.1.
Answer options D and B are incorrect. The DB-9 and DB-25 port types on the computer are used as
serial ports. A DB-9 male type port has 9 pins, whereas a DB-25 male type port has 25 pins.
What is a serial port?
Serial port is the primary means for connecting modems and mouse to a computer. There are two
types of serial port connectors, 9-pin and 25-pin. The word serial refers to the data is sent in series,
one bit at a time, over a single wire. This design is significantly slower than sending 8 bits at a time
via a parallel channel, but serial signals can travel much farther without degradation.