Definition of Computer Architecture

computer architecture - the art of assembling logical elements into a computing device; the specification of the relation between parts of a computer system
computer architecture - (computer science) the structure and organization of a computer's hardware or system software; "the architecture of a computer's system software"
architecture
structure - the manner of construction of something and the arrangement of its parts; "artists must study the structure of the human body"; "the structure of the benzene molecule"

Definition of Encoder

An encoder is a device used to change a signal (such as a bitstream) or data into a code. The code may serve any of a number of purposes such as compressing information for transmission or storage, encrypting or adding redundancies to the input code, or translating from one code to another. This is usually done by means of a programmed algorithm, especially if any part is digital, while most analog encoding is done with analog circuitry.

Don’t Cares during design
Don’t cares arise only in two cases
1) When the designer truly does not care what the output provides.
2) When the input will never occur

DECODER

In digital electronics this would mean that a decoder is a multiple-input, multiple-output logic circuit that converts coded inputs into coded outputs, where the input and output codes are different. e.g. n-to-2ⁿ, BCD decoders.The simplest decoder circuit would be an AND gate because the output of an AND gate is "High" (1) only when all its inputs are "High". The input codegenerally has fewer bits than the output code. Each input code produces a different output code word.

latches

In electronics, a latch is a kind of bistable multivibrator, an electronic circuit which has two stable states and thereby can store one bit of information. Today the word is mainly used for simple transparent storage elements, while slightly more advanced non-transparent (or clocked) devices are described as flip-flops. Informally, as this distinction is quite new, the two words are sometimes used interchangeably.

flipflop

flipflop Also referred to as a bistable gate, a type of circuit that is interconnected with like circuits to form logic gates in digital integrated circuits, such as memory chips and microprocessors. The name “flip-flop” comes from the circuit’s nature of alternating between two states when a current is applied to the circuit (for example, 1 to 0 or 0 to 1). A flip-flop will maintain its state indefinitely until it receives an input pulse, called a trigger, which forces it to alternate its state. Once the circuit changes state it remains in that state until another trigger is received.

fundamental digital definitions

http://dept-info.labri.u-bordeaux.fr/~strandh/Teaching/AMP/Common/Strandh-Tutorial/Dir.html This link contains basic digital definitions