WhatsApp: its role and history
WhatsApp was founded by Jan Koum and Brian Acton in 2009. At the end of the year, it was launched on the App Store for iPhone with no alternatives in the world at the time.
This application, referred to as an instant messenger, was intended to give users an opportunity to exchange messages in real time using mobile Internet or WiFi. Today WhatsApp is available for all popular mobile operating systems.
When somebody asks me a question “what kind of work do you do?" I answer, a "SIM-card software developer”, even well versed in software development people are often surprised. Many people think that the SIM-card is something like a flash drive.
In this article I will briefly tell you about the SIM-card (and smart cards in general), what for it is needed and what it has inside.
In fact, the SIM-card is an instance of a contact smart card with a microprocessor. It represents a fairly secure microcomputer with CPU, ROM (optional), RAM and NVRAM (which stands as a prototype of the hard drive in the PC) with hardware generators of random numbers and hardware implementation of cryptographic algorithms.
The structure of microprocessor smart card can be as: