dvi-i cable clarifiation

while i was reading about dvi-i cables i have seen that it can support both analog video signal and digital video signals.can u explain me about the difference between analog and digital video signals . thanks you

Analog signals are a variable voltages representing the brightness of the pixels, digital is the same but instead of a voltage, a numerical representation of it is sent instead.

CRT monitors used the voltage to directly control the intensity of the beams inside the tube but since LCD and OLED screens have become common which need computer control to address individual pixels, it has become easier to skip the video card conversion of brightness to analog then the monitors analog to brightness and instead connect the digital signal straight through. From a picture quality aspect, there is little if anything between them but using digital does eliminate some of the problems with the high voltages and wide bandwidths amplifiers needed in older CRT monitors. DVI-I and other systems carrying both types are there for compatibility and I would guess will be 'retired' as HDMI takes over.

Brian.

it has become easier to skip the video card conversion of brightness to analog then the monitors analog to brightness and instead connect the digital signal straight through

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One thing i am not clear.As the image are present in binary values in hard disk , then why the video card want to convert brightness to analog rather than converting digital values to analog .sorry if my thought is wrong.Thank you in advance

Bad wording on my part - by brightness I meant the intensity of light which has an equivalent numerical value.

Using analog on a CRT monitor:

data --> video card DAC --> (analog signal cable) --> monitor video amplifier --> CRT

Using analog on an LCD/LED monitor:

data --> video card DAC --> (analog signal cable) --> monitor ADC --> monitor display

Using digital on an LCD/LED:

data --> (digital signal cable) --> monitor display

Note that when using analog on a digital type display it goes through a DAC then and ADC, which means they can be eliminated.

Brian.