What’s an Asynchronous Notification technique? It’s a way of getting the attention of something (a task/process/thread/gerbil) without the task/process/thread/gerbil waiting. Basically an interrupt. Who needs it? To enable a task to respond quickly to a condition detected by another task. … Continue reading →

Essentially Ada’s protected objects encapsulate data and operations, and the operations then have automatic mutual exclusion. Guards can also then be placed on these operations for condition synchronization. They used to be called protected records because the data is like … Continue reading →

For a concurrent program to be correct it needs decent synchronisation (wow, he uses both spellings…he used a ‘z’ in the title which I copy and pasted, and an ‘s’ everywhere else) and communication. Shared variables communication We all know … Continue reading →

Ada task specifications explain how you can communicate with them. The body can be compiled separately from the specification (normal Ada stuff). You can have tasks that have no way of communicating with them (a one-way client type situation). There … Continue reading →

Ada & exception handling The domain of the exception is the block (the begin). Exception propagation. No syntactic relationship between subprograms and exceptions; so the exceptions that might be raised are specified at a package level, not a procedure level. … Continue reading →

There are 6 aspects of Dependability: Availability Reliability Safety; non-onccurrence of catastrophic consequences Confidentiality; security Integrity; information doesn’t get altered improperly Maintainability; system has ability to can be repaired/evolved Reliability of a system is a measure of how successful it … Continue reading →

Most of this was just a recap on ADS. OOP in Ada We wont use OOP in Ada too much. Thankfully. It’s based on type extensions and dynamic polymorphism. So you can do something like: type EA is tagged record … Continue reading →

Terminology Hard real-time: Systems where it is imperative that responses occur within the required deadline, e.g. a flight control system Soft real-time: Systems where it would be useful to know the data immediately, but the data can still be useful … Continue reading →