In terms of the history of the signal, it was the analog signal that came first. That doesn't mean that it can't still be used in conjunction with an analog signal in today's use.
First you start with an idea of what the circuit will do.
Analogue
No, Pulse Code Modulation is a communication method used to carry digital data but is not part of any analog to digital conversion. PCM is often used to carry audio data as a digital stream and therefore is the encoding used as the signal is first converted to a digital format.
First there was analog. Then Digital came along and said 'Get you hands outta my face!' Digital then was born.
The radio has gone through many changes including a switch from analog to digital. The first digital radio was invented in the late 1960s.
digital computers were first used in 1942 analog computers were first used in about 100BC
Digital images are transmitted on computer networks by first compressing them to reduce their size. JPEGs are an example of compressed image files.
Analog computers were first made in the late 1920s, Digital computers were first made in the early 1940s.
CPCD was adopted by companies with analog systems to make them more competitive with digital systems
Analog television was first used in the 1930s. Analog signals are sent by varying voltage, radio frequencies, and static images.
The majority of modern computing devices are digital. That means they work by using many on and off type electrical signals. Analog computers work by using vary ranges of constantly-changing signals in real-time without converting them to digital sequences first.
digital converter extracts samples of analog signal from input siganl digital converter quantizes analog sample and assignes a binary numbervalue to it digital coanverter encodes a quantized analog signal to transmit it across a digital network