Black boxes contain the information regarding to a flight. What is the form of those information? Any particular language log?
There are 2 different black boxes.
The cockpit voice recorder. This holds audio from several different sources, including the microphone for each pilot, the radio and a general cockpit microphone.
The flight data recorder holds at least 88 different parameters including attitude of the craft, engine performance, autopilot setting, pilot input one the controls, etc.
Although I have no specific information on this I do work around electronics/computer for a living so if I had to guess...
The older units most likely ran on slow speed audio tapes of some sort, the quality is not great but you can get a lot of time on a single tape. I don't know how the old ones stored flight data or if they even did but tape format would be an option for that as well.
Modern ones most likely store data in solid state chips or on a platter style hard drive. I would think solid state non volatile memory is used (think SD memory card) as its far less susceptible to shock damage than a platter style hard drive. Since these devices most likely use components made for generic purposes the audio could be encoded at any variety of resolutions but is most likely 44.1Khz/16bit or something like that simply because thats what many A/D converters run at.
The flight data may have some custom data format but is stored in some normalized way like any data set on any computer. Maybe JSON, maybe XLM who knows, but things like GPS data have standard string representations that I would think are used. I would think they use some kind of sequential writing on the memory chip so that if something goes wrong mid memory write they can extract based on specific memory locations. Basically if you know that every write of data takes 1000 bytes and you started writing at address 0 you can grab the data from any point in time by directly addressing the memory location.
At least thats how I would design a black box...