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what is the difference between counters and shift registers?
also how are timers different from counters?

Difference between Counters and Shift Registers -

Counters are Usually numerical counters displayed on some Internet web pages. Once set up, these counters will be incremented one every time the web page is retrieved.

A counter is a special case of a register. Usually, it can only be loaded, stored, or incremented, or used for the stack or as the program counter.


But Shift registers are a type of sequential logic circuit, mainly for storage of digital data. They are a group of flip-flops connected in a chain so that the output from one flip-flop becomes the input of the next flip-flop. Most of the registers possess no characteristic internal sequence of states.


How are timers different from counters?

A timer is a counter that counts clocks automatically and keeps track of time in seconds..

A counter is one that has to be made to count by the programmer whenever needed...


Timer is a "counter", which counts at equal intervals of time (anything from counting system clock to oscillator clocks).

counter in a general name, which counts an event. this event need not be timed equally at all.

I would like to quote some examples to support the definitions given in the previous post.

Counter: The number of views of each thread given in the rightmost column when you open into the general discussion page of the forum is an example of a counter

Shift Register: A sequence of logic gates connected in series, e.g. AND with NOT, usually called NAND. The output from the AND gate (0 or 1) is the input for the NOT gate and the final output comes then (1 or 0, respectively; note that it is a NOT gate, i.e. it is meant to invert the signal it gets, yes to no, no to yes)

Timer: That in your microwave oven. You set the time, then it ticks every second (specific time interval) by 1. Finally, when the set time matches the result of the counter, the bell rings

A register can hold data, and it can be used for temporary storage or, in the case of an accumulator, it can participate in arithmetic or logical operations.
A counter is a special case of a register. Usually, it can only be loaded, stored, or incremented, or used for the stack or as the program counter.

Counters

Counter is the most useful and versatile subsystem of digital branch. Counter is going to count number of clock pulses applied to it. Maximum count that binary counter can count is 2n- 1. Clock pulses occur at regular time interval, so that counter can be used to measure time or frequency. Digital counters are integrated circuits (ICs) that count events in computers and other digital systems. Because they must remember past states, digital counters include memory. Generally, digital counters consist of bistable devices or bistable multi vibrators called flip-flops. The number of flip-flops and the way in which they are connected determines the number of states and the sequence of states that digital counters complete in each full cycle.
Shift registers

Register capable of shifting its binary information in one or both directions is called shift registers. The logical configuration of the shift registers consists of the chain of flip-flops in cascade, with the o/p of one flip-flop connected to input of next flip-flop. All flip-flops receive common clock pulses which activate the shift from one stage to the next.

The output of the flip-flop is connected to the D input of the next flip-flop. Each clock pulse shifts the contents of the register one bit position to the right. The serial input data lines what goes into the leftmost flip-flop during the shift. The serial output is taken from the output of the right most flip-flops. Sometimes it is necessary to control the shift so that it occurs only with certain pulses but not with the others. This can be done by inhibiting the clock from the input of register to prevent it from shifting.


Fig. 6: 4-bit Shift Register
Counters

Counter is the most useful and versatile subsystem of digital branch. Counter is going to count number of clock pulses applied to it. Maximum count that binary counter can count is 2n- 1. Clock pulses occur at regular time interval, so that counter can be used to measure time or frequency. Digital counters are integrated circuits (ICs) that count events in computers and other digital systems. Because they must remember past states, digital counters include memory. Generally, digital counters consist of bistable devices or bistable multi vibrators called flip-flops. The number of flip-flops and the way in which they are connected determines the number of states and the sequence of states that digital counters complete in each full cycle.

Counters can be subdivided into 2 groups:

Asynchronous Counters
Synchronous Counters

The way in which devices are clocked determines whether digital counters are categorized as synchronous or asynchronous. In synchronous devices (such as synchronous BCD counters and synchronous decade counters), one clock triggers all of the flip-flops simultaneously. With asynchronous devices, often called asynchronous ripple counters an external clock pulse triggers only the first first-flop. Each successive flip-flop is then clocked by one of the outputs (Q or Q') of the previous flip-flop. Digital counters are configured as UP (counting in increasing sequence), DOWN (counting in decreasing sequence) or Bidirectional (UP / DOWN).

Synchronous / Asynchronous counter can be subdivided into following subgroups:

Sequential Counters: States of counter are sequential.
Non-sequential Counters: Sequence or states of counter are sequential but irregular.
Regular Counters: In this counters, FFs are used. There is direct relation between number of states and number of FFs used i.e. N=2m.
Decade counter – counts through ten states per stage.
Up down counter – counts both up and down, under command of a control input.
Ring counter – formed by a shift register with feedback connection in a ring.
Johnson counter – a twisted ring counter.
Cascaded counter.

difference between register and counter?

What two principal functions are performed by a shift register?

Create a c program that receives the month and year from the keyboard as integers and display the respective calendar.



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