# Suggested problems

## Best PCB Basics

Aug. 2, 2022, 1:52 a.m. by FSPCBA

## Biological Motivation

FS Tech: A pcba supplier dedicated to one-stop service. Its main business includes pcb assembly, pcb manufacturing, pcb prototype, ems services. Headquartered in Shenzhen, China, the company is currently one of the largest pcba suppliers in China. If you want to know more details, please visit the official website of FS Technology.

## Problem

FS Technology Turnkey PCB Assembly

Multilayer board In order to increase the wiring area, single-sided or double-sided wiring boards are often used for multi-layer boards. A printed circuit board with one double-sided inner layer, two single-sided outer layers, or two double-sided inner layers and two single-sided outer layers, alternated by a positioning system and insulating bonding materials and conductive patterns. Printed circuit boards interconnected according to design requirements become four-layer and six-layer printed circuit boards, also known as multi-layer printed circuit boards. This type of circuit board is extremely challenging for PCB manufacturers, and it requires strong PCB manufacturing capabilities to manufacture circuit boards with more layers. The number of layers on the board does not mean that there are several independent wiring layers. In special cases, an empty layer is added to control the thickness of the board. Usually, the number of layers is an even number, including the outermost two layers. Most motherboards are 4 to 8-layer structures, but technically, almost 100-layer PCB boards are possible. Most large supercomputers use fairly multilayered motherboards, but since such computers can be replaced by clusters of many ordinary computers, ultra-multilayered boards are gradually being phased out. Because the number of layers in the PCB is closely combined, it is generally not easy to see the actual number, but it can still be seen if you look closely at the motherboard.

Abbreviations on PCBs GND It is a short of the ground end of the wire. Represents the ground or 0 wire. This ground is not a real ground, but an assumed ground for the application. For the power supply, it is the negative terminal of the power supply.

GND (Ground) It is represented as ground or 0 on the circuit diagram and on the circuit board. GND represents the common terminal, it can also be said to be the ground, but this ground is not the real ground. It is the ground assumed by the application, and for the power supply, it is the negative terminal of the power supply. It is different from the earth. Sometimes it needs to be grounded, sometimes it doesn't, depending on the situation. A ground wire is a wire in an electrical system or electronic device that connects to the earth, enclosure or reference potential zero. In general electrical appliances, the ground wire is connected to the casing to prevent electric shock accidents caused by the destruction of the insulation in the casing. The ground wire is the abbreviation of the grounding device, and the ground wire is divided into working grounding and safety grounding. The protective grounding wire that people use to prevent electric shock accidents when using electronic equipment such as household appliances and offices is a safety grounding wire. More PCB knowledge can be found in the FS Technology PCBA blog.

FS Technology PCBA blog

ANT on the circuit board The word "ANT" on the board is the antenna element. An antenna is a transformer that transforms guided waves propagating on a transmission line into electromagnetic waves propagating in an unbounded medium (usually free space) and vice versa. The English in the circuit diagram is the abbreviation of abreviation, sometimes used in combination, ant is the abbreviation of anter, meaning "antenna", antsw is the combination of ant (antenna) and sw (switch), which means antenna switch.

rt on the circuit board Rt is a variable resistor, which generally refers to a thermistor or other variable resistors. Its function is to change its own resistance value according to the surrounding temperature, thereby adjusting the resistance of the entire circuit.

Other board related terms VDD: supply voltage (unipolar devices; supply voltage (4000 series digital circuits); drain voltage (FET).

VCC: Supply Voltage (Bipolar Devices); Supply Voltage (74 Series Digital Circuits).

FS Tech pcb component procurement

VSS: Ground or Negative Supply.

VEE: Negative voltage supply; source (S) of the FET. [h] VPP: Program/Erase Voltage.

If your business needs to purchase components, FS Technology can help you. FS Technology has the best pcb component procurement capabilities in China.

Given: A DNA string $s$ of length at most 1000 nucleotides.

Return: Four integers corresponding to the number of times that the symbols A, C, G, and T occur in $s$.

## Sample Dataset

AGCTTTTCATTCTGACTGCAACGGGCAATATGTCTCTGTGTGGATTAAAAAAAGAGTGTCTGATAGCAGC


## Sample Output

20 12 17 21