For example, what do I need in simple Z ?

In simple Z, you will need a text editor to write your Z specifications, a Z tool such as Z/EVES or CZT to typecheck and validate your specifications, and a basic understanding of the Z notation and its syntax. Additionally, you may also need a formal methods background to effectively use Z for software specification and verification.

In simple Z, you need:

1. Constants and variables: Constants are unchanging values, while variables can change their values. In simple Z, you can declare constants and variables using the `const` and `var` keywords, respectively. For example:

```z
const pi = 3.14159;
var x = 5;
```

2. Data types: Simple Z supports a variety of data types, including integers, floating-point numbers, strings, and booleans. You can specify the data type of a constant or variable when you declare it. For example:

```z
const pi = 3.14159; // Floating-point number
var x = 5; // Integer
var name = "John Doe"; // String
var is_true = true; // Boolean
```

3. Operators: Simple Z supports a variety of operators, including arithmetic operators, comparison operators, and logical operators. For example:

```z
const a = 5;
const b = 3;

console.log(a + b); // 8
console.log(a - b); // 2
console.log(a - b); // 15
console.log(a / b); // 1.6666666666666667
console.log(a % b); // 2
console.log(a == b); // false
console.log(a != b); // true
console.log(a > b); // true
console.log(a < b); // false
console.log(a >= b); // true
console.log(a <= b); // false
```

4. Functions: Functions are reusable blocks of code that can be called from other parts of your program. In simple Z, you can define functions using the `function` keyword. For example:

```z
function sum(a, b) {
return a + b;
}

console.log(sum(5, 3)); // 8
```

5. Control flow: Simple Z supports a variety of control flow statements, including `if`, `else`, `while`, and `for`. These statements allow you to control the flow of execution in your program. For example:

```z
const a = 5;

if (a > 0) {
console.log("a is greater than 0");
} else {
console.log("a is less than or equal to 0");
}

// Output: a is greater than 0
```

```z
const a = 10;

while (a > 0) {
console.log(a);
a--;
}

// Output:
// 10
// 9
// 8
// 7
// 6
// 5
// 4
// 3
// 2
// 1
```

6. Input and output: Simple Z provides functions for reading input from the user and writing output to the console. You can use the `console.log()` function to write output to the console, and the `console.readLine()` function to read input from the user. For example:

```z
const name = console.readLine();

console.log("Hello, " + name + "!");
```

These are just the basics of simple Z. For more information, you can refer to the official documentation or find tutorials online.