The components are housed in a perforated, strong, or robust plastic shell. They are filled with rubber buttons that press into the openings. When pressed, the buttons below them complete a circuit and send electrical impulses across a circuit board. They are designated with numbers and operating symbols. The calculator's brain is the microprocessor, an integrated device that houses an entire Central Processing Unit (CPU) on a single silicon microchip. The CPU interprets pushed buttons and works with binary numbers, which are sequences of "1"s and "0"s. This is the only language the CPU is capable of understanding. Before completing the required operation, the CPU will temporarily store the binary inputs in its registers. After that, the binary output is converted to a decimal and shown once more. A pattern is created by rearrangement of light molecules and shown on an LCD panel as the output. LED displays were used in earlier iterations, which used more electricity. Both the calculator's output and the inputted numbers are displayed as they are being entered. Strong lithium batteries or reusable solar cells that replenish the device as photons are received throughout the day power calculators. To create logic gates, the transistors are paired in precise ways. These logic gates provide particular outputs based on the positioning of these transistors. And, or, and NOT gates are the most fundamental ones. Our knowledge of transistors and logic gates will be greatly facilitated by our analogy of transistors as taps. It is instructive to know that the CPU just draws these numbers for our convenience and does not turn them into binary bits. The button or input is recognized by the CPU via the circuit path, and its binary value is stored. For instance, the binary representation of 2 is 10. Every time you enter data or need the outcomes of an action displayed, it transforms binary to decimal. You only need to be aware that the processor uses circuits to convert numbers and carry out operations on a train of '1's and '0's at this time because explaining how numbers are converted to various systems would take too much time and be irrelevant. While the OR gate uses two transistors connected in parallel to accomplish logical disjunction, the AND gate uses transistors in a series configuration to perform logical conjunction. Simply put, the NOT gate negates the input, turning a "1" into a "0," and vice versa. Another significant logic gate, the exclusive-OR gate, can be created by combining these gates. This gate gives the idea that its two inputs are being added. Simple EX-OR operations result in a "1" when their inputs are different. Millions of these logic gates are arranged in a specific way in a calculator to conduct intricate computations on input numbers. Although the result of adding "1" and "1" is "0," one can see from the final set of inputs for an EX-OR gate that it additionally produces a carry bit that is not listed in our table.

Another bit is produced by the circuit and "carried over" into the memory as an additional bit. Actually, the bits are divided into two columns: total and carry. However, the circuit once more disregards any carry over bit that has been sent to it by a prior adder. A full adder is a three-input adder that takes into account carry-overs from earlier adders. Three "1s" generate a "1" with a "1" carry as well, and two "1s" generate a "0" with a "1" carry. The following adder receives the carry out bit. The complete adder can be thought of as two half adders combined, or as a mixture of other logic gates. Although it is challenging to construct binary multiplication using gates, the operation is similar to decimal multiplication. Additionally, two times as many output bits as seeded input bits are produced. Therefore, the operation can be carried out using a technique known as partial product accumulation. In the example, the sums that result from multiplying two 2-bit values, A and B, are the sums of the products of the individual bits.

Four AND gates produce the various products. Additionally, these sums can be added using half adders to yield the sums S4–S0, which can then be combined to give S, the sum of the products of A and B. Similar to this, an 8-bit number can be created by multiplying two 4-bit values using 16 AND gates and 12 adders, and so on. Using identical logic gates, the calculator can also subtract and divide numbers. It is crucial to understand that we have only briefly discussed the most fundamental or elementary circuits for addition and multiplication in order to give you a general concept. These circuits have long since been replaced by ones that operate much more quickly. The general purpose computing performed by a computer, which is mostly comprised of calculations and number crunching, is accomplished using the exact same logic gates. The calculator is not programmable; it merely performs calculations. The number of operations that a calculator could perform increased as more transistors were added to a processor. Calculators are now much more sophisticated and scientific, have more memory and better processors, and are used by professionals like engineers who can consequently conduct calculus and logarithmic calculations. And now, this gadget—along with a great number of others—is merged with our cherished cellphones.