Do you want to work as an embedded engineer? You're reading the right blog, then. In this blog post about Embedded C interview questions, we list some of the questions along with the detailed answers that interviewers might ask. These top Embedded C interview questions and answers were made by MindMajix experts who have worked in the embedded field for more than a decade.
Embedded C is the most popular language used in the development of electronic devices. Embedded software is associated with every electrical device's central processing unit. Embedded C code significantly impacts the speed with which a CPU completes a given task. Daily, we rely on our mobile phones, washing machines, digital cameras, etc., all of which are examples of technical devices. All of these gadgets rely on a microcontroller that was programmed in embedded C.
To understand all the concepts of Embedded C to crack the interview, we have listed frequently asked interview questions into three categories below. Check now.
A group of language modifications for the C programming language that the C Standards Committee has approved are known as embedded C. It is typically employed to address compatibility problems among C extensions for various embedded systems. In order to enable advanced microprocessor features like fixed-point arithmetic, several separate memory banks, and fundamental I/O operations, embedded C programming generally necessitates nonstandard additions to the C language.
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A microprocessor-based computer and software system that is specifically created to carry out a single task is known as an embedded system. Either acting alone or as a component of a larger system, an embedded system.
C is a high-level programming language that can be used to make desktop programmes for any purpose. Embedded C, on the other hand, is a form of the C programming language that is used to make software for microcontrollers. "Embedded" in this case refers to the host computer or microcontroller, not the programming language.
Not a fundamental programming language, embedded C. It is a C programming language extension used to create software for microcontrollers. The additions made to the standard C programming language in embedded C include fixed-point arithmetic operations, address space access, I/O Hardware Addressing, etc.
The expansion of the C programming language is called embedded C. Here are Embedded C's main benefits:
Volatile is a type qualifier in embedded C that tells the compiler not to optimize the objects. The C standard says that the tumultuous type object can be changed in ways that the implementation doesn't know about. In other words, the value of an object marked as volatile can be changed at any time without having to change the code. Every time a programme calls on a volatile object, the compiler will reload the value from memory. Memory reading is the only way to confirm that the value has changed without reason.
A segmentation fault error can happen during programme execution for a variety of reasons.
Interrupt Service Routines, or ISR, is what it means in Embedded C. These are the programmes that are stored at certain addresses in memory and run when certain types of interrupts happen.
If a programme attempts to access memory past the maximum amount of available memory in C, a stack overrun error may result. For instance, if a pointer goes beyond the stack's maximum size, the stacking overflow error could happen (boundaries). When a stack overflowing error occurs, the application stops and no more instructions are carried out. Therefore, when employing the pointer and limit borders, we must exercise extreme caution. Stack overflow errors are produced as a result of segmentation fault errors.
No. It is not able to move a parameter and have the ISR return a value. The ISR does not accept any parameters and does not return anything. When a software or hardware event takes place and the code doesn't really call an ISR, it is called instead. No parameters are therefore supplied into an ISR. There is no contact code to access the ISR's returned values because the code does not call the ISR. An ISR does not therefore return any value.
The amount of clock cycles that the processor needs to reply to an interruption request is known as the interrupt latency. This clock cycle counts the number of clock cycles between the assertions in the interrupt request and the first instruction in the interrupt handler.
The oscilloscope can be used to measure the interruption latency in Embedded C. Observe the instructions below:
In Embedded C, the interrupt latency can be decreased in a number of ways. Numerous factors affect the interrupt latency. Here is a list of a few of them:
So, we can simply lower the interrupt latency by choosing the right platform and processor. We can also decrease the interrupt latency by shortening the ISR and avoiding calling a function inside of it.
Static variables get the advantage of holding onto their value even when used outside their intended context. This implies that we can only initialize static variables once. Local in scope, yet lasting over the duration of the programme. The variable is kept around by the compiler until the end of the programme. Static variables may be defined either inside or outside of the function. Static variables have zero as their default value. Static variables continue to exist during programme execution.
Syntax: static datatype variable_name = value;
In most cases, a static constant is used to count an object. For instance, whenever a second account opens in the bank, the function openBakAccount() is called. Then, we can create a static variable in the method and increment it with each function run to keep track of the overall number of opened accounts.
By mistakenly changing the pointer address, we can protect a character pointer by using the constant character pointer (const char*). With the string's pointer address, it avoids pointless modifications.
A variable that may be accessed from another file can be declared with the "extern" keyboard shortcut. This is how a variable in one source file that is defined in that other source file might be used.
A pointer that refers to a function rather than a variable is called a function pointer. A function pointer is entirely distinct from the class of many other pointers because of this. A function pointer saves the address of a certain function so that a programme can use it by calling the function.
Indeed, a C variable can serve as both a dynamic and a static one. It's possible to make use of both stable and dynamic variables at the same time. GPIO registers are accessed using a combination of volatile and const variables. If a switch or other output device is wired to GPIO in this way, the value of the port will be affected by "external factors." Important as it may seem, the volatile variable prevents the compiler from assuming anything and assures that the value is always read from the GPIO location.
A pointer that directs the user to a memory address that has already been freed by the program and is no longer in use is known as a dangling pointer. Dangling pointers are initialized pointers that have been left hanging because the programmers occasionally forget to initialize them with a valid address. When an object is deleted or released from memory without changing the value of the pointer, this results in dangling pointers. A runtime error could occur if you attempt to describe the various dangling pointers.
For a 64-bit CPU, a size letter takes up 1 byte, an integer 4 bytes, an integer reference 4 bytes, and a character pointer 8 bytes.
Embedded Processor real-time applications include the following:
Following are a few instances of embedded systems that can be used in aerospace applications:
A macro named NULL is defined in C. A pointer that points nowhere useful is known as a null pointer. When we want to make sure that perhaps the pointer doesn't really point to every legitimate address and we don't want to use it to modify anything, we define the NULL pointer. We cannot determine whether this pointer refers to a legitimate address or not without using a null pointer.
Yes, countdown to zero loops were preferable to count up loops because the compiler can optimize the comparison to zero at loop termination. The majority of processors include instructions for zero comparison. As a result, they can simply remove the loop variable from the maximum value before comparing it to zero. Because of this, countdown to zero loops were preferable.
Here are a few instances of embedded systems being used in automobile applications:
Structure padding is a concept utilized in the C programming language. The memory contents are brought into sync by inserting one or more zero bytes between the addresses. The compiler routinely checks to ensure that all of its parts are properly byte aligned.
Here are a few examples of medical devices that make use of embedded systems:
The language of the computer, not the programmer, is called Machine Code. Machine language or object code is the only kind of instruction that a computer will accept. The code is complicated and prone to mistakes when a coder analyzes it. All software, whether written in languages like C, C++, or Java, must eventually be converted into machine code so that the computer can run it.
As a general rule, the speed at which the application executes depends directly on the oscillator frequency. Therefore, in most circumstances, increasing the oscillator frequency will result in double the application speed.
Million Instructions Per Second is referred to as MIPS. It is a rough indicator of the unprocessed processing power of a computer. Because measurement methods frequently vary and because different computers may need various sets of instructions to do the same task, it could be misleading.
Increasing the clock frequency is the simplest approach to make the 8051 microcontrollers work better. The original devices' 12MHz maximum clock speed restriction is greatly exceeded by the 8051 microcontrollers. The best technique to boost performance is to modify the microcontroller's internal architecture so that less oscillator cycles are needed to complete each machine instruction.
Utilizing dynamic memory allocation causes a problem known as memory fragmentation. Our in-use variables are dispersed throughout the RAM as we repeatedly allocate and release memory spaces over time, resulting in non-contiguous free memory blocks. Memory fragmentation is the term for this. Failure of dynamic memory allocation may result from this. A runtime error results, for instance, if you need to allocate space for an array of 100 integers but there isn't a continuous block of memory that has that much room. Because of this, firmware for embedded devices never uses dynamic memory allocation.
With smaller definitions than other sorts of functions, inline functions can be substituted where their function call occurred. With the keyword __inline, ARM compilers enable inline functions. These procedures have a brief definition, and each time the inline function is called, the method body is used instead.
The types of memory used in an embedded device written in C are as follows:
To improve the efficiency of the embedded system, C provides machine instructions that are optimized for the input. Since most high-level languages make use of libraries, they increase the amount of storage space needed, which is problematic for embedded devices.
Embedded C is not as hard as other languages, but it is not easy to read or change.
Although it was not initially intended for embedded software development, the C programming language supports a variety of programming methods, from high-level application code to direct manipulation of hardware registers. Consequently, C is now the most used programming language for embedded devices.
For Embedded C, a specific compiler is used that can make output for specific hardware/microcontrollers. Popular compiler to run a program written in the Embedded C language is the Keil compiler.
There are three different types of data for integers that can be used with embedded C: int, short, and long.
Embedded C is usually used to make applications for microcontrollers. C is a high-level language for programming. Embedded C is just a form of the C language that lets you add more features. This programming language works with any hardware.
The C startup code is used to set up things like global data variables and memory for data. It also sets a part of the data memory to 0 for variables that aren't set up yet when the programme loads.
Developers use keywords to tell the programme where the pins are located. The programme uses standard keywords like bit, sbit, SFR, etc. to declare the bits and single pins. These keywords are already set up in the embedded C programme.
A microcontroller is used to manage and control the functions of each embedded system. Embedded C is an addition to the C programming language, making it easier to make embedded systems. In other words, it helps to code systems that use microcontrollers.
When a variable is declared, the volatile keyword is added as a qualifier. It tells the compiler that the value of the variable could change at any time, even if the code it finds nearby doesn't do anything.
|Related Article : Embedded Software Engineer Interview Questions.|
Embedded C is the most popular language for making embedded systems because it is easy to use, works well, can be made quickly and works with other systems. To beat this embedded system interview competition, know all these embedded system interview questions and prepare well to ace the interview and land an embedded engineer job.
To prepare more, just enroll your names in Selenium with C training courses to improve the skills and knowledge required for an interview.
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Madhuri is a Senior Content Creator at MindMajix. She has written about a range of different topics on various technologies, which include, Splunk, Tensorflow, Selenium, and CEH. She spends most of her time researching on technology, and startups. Connect with her via LinkedIn and Twitter .
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