What are the functions and working methods of PLC programmers?

Programmer is an important peripheral equipment of PLC. User program is sent into the memory of PLC by programmer. Programmer can also be used to check the program, modify the program and monitor the working status of PLC.
Common devices for programming PLC include hand-held programmer and computer programming.
In the early development of programmable controller, special programmer was used to program. Small programmable controllers use cheap and portable hand-held programmers, while large and medium-sized programmable controllers use portable programmers with small CRTs as displays. The special programmer can only program some products of a certain manufacturer, and its application range is limited. Handheld programmer can not directly input and edit ladder diagram, but can only input and edit instructions, but it has the advantages of small size, easy to carry, can be used for on-site debugging, low price.
With the popularity of computers, more and more users use personal computer-based programming software. At present, the programmable controller manufacturer or distributor provides programmable software to the user. By adding appropriate hardware interface and software package to the personal computer, the PLC can be programmed by the personal computer. Using a computer as a programmer, the ladder diagram can be directly compiled and displayed. The program can be saved, printed and debugged, which is very helpful for finding faults.