Blockchain Blockchain Other Certification CBDE Questions & Answers

• Question 51:

  Function and Variable Visibility:

  A. a function that is marked as internal cannot be called by other contracts, unless the function is used by a derived contract. Private Functions cannot be called by any other outside contract and public variables are generating automatically a getter function.

  B. a function that is marked as external can never be called internally. Private functions can also be called by derived contracts using inheritance. Private variables are accessible also in derived contracts.

  Correct Answer: A

• Question 52:

  A Mapping consists of keys and value.

  A. the Keys can be anything, but the value can't be another mapping or struct.

  B. the Value can be anything, but the key cannot be another mapping, struct, integer or Boolean.

  C. the value can be anything, but the key cannot be another mapping, struct, enum or dynamically sized array.

  Correct Answer: C

• Question 53:

  To Iterate through a mapping, you:

  A. can use the length parameter of the mapping.

  B. you need an external helper variable.

  C. you cannot iterate any mapping to make the overall language design more safe.

  Correct Answer: B

• Question 54:

  A Struct is a great way:

  A. to define a new datatype in Solidity, so you don't need to use objects of another contract.

  B. to hold instances of other contracts.

  C. to implement pointers to other contracts that can hold new datatypes.

  Correct Answer: A

• Question 55:

  If we divide two integers: 5/2, the result is: A. 2, because the decimal is truncated.

  B. 3, because it's always rounded.

  C. 2.5, because it's automatically converted into a float.

  Correct Answer: A

• Question 56:

  The following are value types in Solidity.

  A. Integer, Boolean, Struct, Mapping and Enum.

  B. Integer, Boolean, Enum and Addresses.

  C. Integer, Boolean, Structs and Fixed Point Numbers.

  Correct Answer: B

• Question 57:

  To compare a String in Solidity you use:

  A. string1 == string2

  B. the internal function "str_compare(str1,str2)"

  C. you can't directly compare two strings, but one method would be to hash both strings and compare the hashes.

  D. bytes32(string1) == bytes32(string2)

  Correct Answer: C

• Question 58:

  Single line comments in Solidity are:

  A. working with either // or ///

  B. working with /* comment */ or /** @.. natspec style */

  C. not possible, all comments must be multi-line.

  Correct Answer: A

• Question 59:

  Multi-Line Comments in Solidity are:

  A. working with either // or ///

  B. working with /* comment */ or /** @.. natspec style */

  C. not possible, all comments must be single-line.

  Correct Answer: B

• Question 60:

  Importing from GitHub:

  A. works across all compilers and platforms the same way.

  B. is generally possible, but currently works only in Remix, but doesn't work in Truffle.

  Correct Answer: B