Hello Manisha,

1. CRO is the acronym for Cathode Ray Oscilloscope. It is an electronic test instrument that graphically displays varying signal voltages.

• A typical CRO is divided into four sections: The display, Vertical controls, Horizontal controls and trigger controls.
• The display is generally a CRT or LCD panel laid out with horizontal and vertical lines known as graticules.
• The vertical section controls the amplitude of the input signal. It has a Volt/Div. knob,  AC / DC / Ground Selector switch and the vertical input for the instrument.
• The horizontal sections contains a time base or sweep of the instrument. The primary control is the Sec / Div. selector switch. It also includes the horizontal input for the device.
• The trigger section controls the start event of the sweep. The trigger can be set to automatically restart after each sweep, or can be configured to respond to an internal or external event. The principal controls of this section are the source and coupling selector switches, and an external trigger input (EXT Input) and level adjustment.
  

2. The front panel control contains the following controls:

• Focus control
• Intensity Control
• Astigmatism
• Beam Finder
• Graticule
• Time Base Control
• Hold off control
• Vertical Sensitivity Control
• Horizontal Sensitivity Control
• Vertical Position Control
• Horizontal Position Control
• Dual Trace Control
• Delayed Sweep Control
• Sweep Trigger Controls

3. The applications of CRO are:

• Measurement of Voltage
• Measurement of Current
• Measurement of Phase
• Measurement of Frequency

Best Wishes.