There are two methods to solve the circuit macroscopically: one is equivalent transformation method, and the other is programming method. (1) Using equivalent transformation, the circuit is simplified step by step, and Ohm's Law (VCR) and Ohm's Law of the whole circuit are applied for calculation (including simple KCL and KVL), and finally unknown current and voltage are obtained. Equivalent transformation methods include series-parallel connection of resistors, Y-△ transformation of resistors, series-parallel connection of power supplies, equivalent transformation of voltage source and current source, Thevenin equivalent transformation, etc. The equivalent transformation method changed the circuit structure. (2) The programming method does not need to change the circuit structure, and the analytical circuit has a fixed program, which is suitable for any linear circuit and easy to be solved by mathematical software. Taking branch current as an example, ① set the reference direction of each branch current, ② write KCL, KVL equation and VCR relationship, and write controlled power source's auxiliary equation. If the initial value equation is added to the differential equation, ③ input the equations into the mathematical software of the computer to find the unknown quantity (or unknown function). Resistance circuit corresponds to real coefficient linear equations, sinusoidal steady-state circuit corresponds to complex coefficient linear equations, and time domain circuit corresponds to linear differential equations. ■ In the era when computers are not popular, in the operation of printing books in traditional teaching, in the face of less complicated circuits and occasions where computers are not allowed to be used (such as exams), the equivalent transformation method of circuits is usually adopted. This method uses ohm's law more after converting the original circuit into a simple circuit, which weakens the core position of KCL and KVL. Large-scale circuits cannot use equivalent transformation method, but only programming method. The programming method makes us really feel the core position of KCL, KVL and VCR (correlation and non-correlation) in solving circuits.