# L&T Technology Services Core CS Questions with Answers

8 previously-asked core cs questions from L&T Technology Services's hiring process, each with the correct answer and a worked explanation. Written against the company's actual test pattern.

_Source: Astra (https://useastra.in). Updated 2026-09-05._

### 1. Which logic gate is known as a universal gate?

A. AND
B. OR
C. NAND
D. XOR

**Answer:** NAND

**Explanation:** NAND (and NOR) can implement any logic function, so it is called a universal gate.

### 2. According to Ohms law, voltage V equals?

A. I * R
B. I / R
C. I + R
D. I - R

**Answer:** I * R

**Explanation:** Ohms law states V = I * R, where I is current and R is resistance.

### 3. Depth first search (DFS) is typically implemented using which data structure?

A. Queue
B. Stack
C. Heap
D. Array

**Answer:** Stack

**Explanation:** DFS uses a stack (or recursion, which uses the call stack) to backtrack.

### 4. In Java, which keyword prevents a class from being inherited?

A. static
B. final
C. abstract
D. private

**Answer:** final

**Explanation:** A class declared final cannot be extended by any subclass.

### 5. Which SQL join returns all rows from the left table plus matching rows from the right?

A. Inner join
B. Left join
C. Right join
D. Cross join

**Answer:** Left join

**Explanation:** A left join keeps every row from the left table and fills unmatched right columns with null.

### 6. Which memory management scheme mainly suffers from external fragmentation?

A. Paging
B. Segmentation
C. Virtual memory
D. Caching

**Answer:** Segmentation

**Explanation:** Variable sized segments leave scattered free gaps, causing external fragmentation; paging causes internal fragmentation.

### 7. In C, what does the & operator return when applied to a variable?

A. its memory address
B. its value
C. its type
D. its size

**Answer:** its memory address

**Explanation:** The address-of operator & yields the memory address of the variable.

### 8. How many bits are there in an IPv4 address?

A. 16
B. 32
C. 64
D. 128

**Answer:** 32

**Explanation:** An IPv4 address is 32 bits, usually written as four 8-bit octets.

More L&T Technology Services preparation, including the full recruitment process: https://useastra.in/campus/ltts